CretaサポートHow do I post in a club?
まだ日本語では提供されていないため、原文で表示しています。上のメニューから翻訳できます。
You need to be an approved member. Open the club, choose the thread you want to post in, and create your post there.
A thread is a board inside the club — the club's admins create them and decide who can read and write in each, so a thread you cannot post in is usually reserved for a higher role rather than broken.
If there is no create button at all, check you are approved rather than pending, and that you are looking at a thread that accepts your role.