No you don't need to be to enter. If you want to vote, then yes you do.
Just go to the contest and post a photo as a reply to the thread. I find it much easier to post via Photobucket. What you would do is scroll down to the reply area then go to the "advanced". You can then scroll down and you will see two ways to attach a photo. Once you do it, it is a piece of cake from then on.
Can't wait to see your photo.