Placing a promotion for your forum, or a discussion or event in it, is easy.
First you want to title your post so people will know what it's about.
Examples of post title:
Forum Name, or Forum Name: Discussion or Event
Next you want to make sure you give a good description of your forum or event.
Include links to your forum and any discussions you're promoting. Otherwise people might not find them.
If you're still not sure about how to post a promotion, look over the board. Some just use a copy of their forum's start page, and maybe make a few adjusts. Like including links to the forum somewhere in it.
Remember this promotions forum is for Beehive forums on this site and other Beehive forum sites on the web only. All others will be removed.
Happy promoting! :-D