I know we've seen alot of questions about this and I'd like to help.
To Join a contest, go to the right sidebar where you see alot of ads. The first box over there should have a picture of a betta fish, (Last month's winner), and a few links in that box. there should be one that says something like, "Join This Months Contest". Upload a picture and check back in a few days to vote. To vote, click on the link in there that says something like "Vote Now!" Or "Vote Today!" Click on the pic you think is the best and wait until the winner is announce the first day of the month.
Hope That Clears Things Up A Little!