Hey Happy, you compete in the rolling forum contest by posting in the latest thread. Even once the competition is closed on a Sunday night UK time (as with this week's competition) your posts will still count towards the upcoming week's competition, so please do get posting in that thread!
Anyone who posts at the randomly chosen time, or within 2 minutes either side of it will win that week's prize. In the case of a closed competition, as currently, your post will count towards the next competition, so the prize may vary from the one stated at the start of the thread. A new thread will be posted sometime today, and the winner(s) of the closed competition announced. However, as previously mentioned, you can already enter the new competition by posting in the existing (latest) thread