I am no expert as we started with the crate the day we got Harlea, but after a quick search you will want to start out slowly for short periods of time and build up to the longer periods. Here is an article I found that might help.
Crate Training an Older Dog
You Can Teach an Old Dog New Tricks
By Arlene Mason
Crating an older dog can be challenging at best, because older dogs have developed bad habits that are hard to break. They can be set in their own ways and often resistant to change. On the other hand if you have developed a good relationship with your dog, then she will be eager to please you and thus, do what you ask of her more readily. Whatever your reasons are to crate train your dog, and whatever her experience, you must exercise patience. Your older dog will not learn as quickly as a puppy, and she may forget more easily. Give her compassion, and love through out the process.
Crate training is the term applied to training your dog to go to one certain place, usually a kennel (or crate) to sleep, for travel, or just to get her out of the way when guests arrive. An older dog, that is no longer a puppy, may need to be crated when you are not at home if she is destructive. Some older dogs may urinate or defecate around the house if not crated; this might be an indication of a medical problem, so be sure to have your dog checked by a veterinarian to rule this out. Another reason to crate Fluffy would be to allow her "quiet time" away from the children. She may also be fearful of things, such as thunder, and the crate would give her a place to hide and feel safe. It is much more dignified for Roscoe the Rotweiler to sit in his crate, than to cower under the bed during a thunderstorm.
Crates range in size and type from small plastic totes to large wire cages. The size and type of crate is up to you. But, you should consider the size and breed of your dog when choosing one. For instance, if you have a Toy Poodle, you do not want a crate that is so large you can stand up in it. By the same token, you do not want a tiny crate for Roscoe the Rotweiler. Ideally, you dog should be able to walk in, turn around and lay down comfortably. This is a good rule of thumb for most dog breeds. There are some breeds, such as the Chow Chow (as well as some individual dogs), that may have a problem with feeling closed in. They may become very stressed when confined in a small area. In this case you will need to select a crate with a very high ceiling, or none at all. You may want to try a large wire cage for this type of dog, or consider using a spare bathroom or laundry room if your dog needs more space.
Eventually, when your dog is comfortable with her crate, she will come to think of it as her den. Thus, a crate that is too big will not allow her to feel secure, nor hold in her body heat; while one that is too small will make her feel cramped.Take her with you when you chose a crate, so that you will be sure to get the right size and she will feel included in the decision.
Now that you and Fluffy have selected a crate, the real work begins.
Fluffy may not want to go into the crate once you get it home. Do NOT force her!
Start by leaving the crate somewhere with the door open. She may go in out of curiosity, let her. She may go in and out as a game. Let her do that too. Let her get used to the crate being in her house. Let her know that it's not a big deal, but that it's not going away, either.
Begin to feed her in the crate after a day or two. First leave the door open so she can come and go as she pleases. With her food in there it will give her a sense of ownership. Soon she will think of it as her crate. Gradually, shut the door, first while she is eating, then open it to allow her to leave. Slowly increase the time she spends in her crate, a little at a time. Go away when the door is closed. Open it when you return. This will reinforce to her that she goes into her crate when you are gone, and that you will never forget about her.
Do NOT spank her and then put her in her crate. The crate can not represent a punishment. If she sees it that way then it will be of no use. She needs to feel safe and secure in her crate. That way when she goes in there she will want to stay. She may even come to think of the crate as her "room". She may even go to her crate without being asked. When she is asked she will enjoy the experience. Always be sure to allow Fluffy to go outside after she has spent time in her crate. This reduces house-soiling accidents. Speaking of accidents, if she has one in her crate, do NOT clean it up immediately. Let her stay in there with it for an hour or more, the longer the better. This way she will realize soiling her crate is unacceptable, you won't always be there to clean it up, and she will NEVER do it again. Be sure you keep children away from the crate while the dog is in there. This could frighten or agitate the dog and she may not feel safe in her crate with children beating on it or kicking it. Also, if children or other dogs are allowed to go into Fluffy's crate, she may not appreciate it. If she is an alpha dog (i.e. very possessive) someone may get hurt as she tries to defend her territory. If she doesn't feel possessive about the crate, then she may no longer want to use it, if someone else is. She would no longer see it as hers. The best thing to do is impress upon everyone in the house that the crate is Fluffy's and no one else's.
Along with Fluffy liking her crate, she needs to know that there are times when she must go in at your request.
Practice this by saying, "Kennel Up" and placing her in the crate. Then praise and/or reward her. Soon you can say "Kennel Up" and she will get into her crate by herself. The "Kennel Up" command is standard and used by groomers and veterinarians to get animals in cages. However, if you have children you may be more comfortable with "Go to your room". There is nothing more amazing than saying, "Go to your room" and seeing the children and the dog going off to their respective rooms. Just shut the doors and relax. Whatever command you use, be consistent. Do NOT confuse the dog with multiple expressions for the same thing. Also, make sure everyone in the household knows the appropriate command, so Fluffy will have no doubt what is required of her.
To successfully crate train an older dog you want a crate that is comfortable and secure. You want to exercise patience and understanding, but be firm and do not give in. Also be kind; if Fluffy really wants out, let her out. Try again later. She'll get the picture eventually. These things take time. Lastly, you want to be consistent. Practice everyday, and multiple times a day. Some dogs are more stubborn than others are and the key is you. Between you and Fluffy, you should have a great crate training experience.