No, you have to specifically may a post for the entry.
See some of other people's as example or one of mine but I warn you I won nothing so far. :-)
Here's the link for the theme annoucement and you see the rules there as well:
https://steemit.com/steemitphotochallenge/@jamtaylor/steemit-photo-challenge-6-theme-announcement-new-giveaway-or-aug-25-28