Hi,
When you post a new picture you have an option to select whether or not it is a competition entry. It will then automatically enter the competition entry list.
The pictures for the competition must be of Ayu Beat. Convert, paint her any way you want, put her in a diorama, we don't care. As long as she's in there somewhere, the entry counts. The entry closing date is when no new entries will be accepted (the Competition box disappears). Voting closing date is when votes will no longer count towards the final score. There are no "official" judges, just the denizens of CoolMiniOrNot!
P.S. the automatic entry was broken for a while but it's been fixed, so name it whatever you want, just make sure when you upload your entry that you select the correct (and only) competiton. The default is "NONE".