how the heck do you compose a topic in the developer forums?
dev forum help
click "New Topic" honestly it's not that hard.
You can not post or reply at bthe official devforums of ROBLOX. Only developers who are enough popular can do so. Once you create a good game and you get known, ROBLOX will contact you saying that you now have post permissions at devforums.
As a summary, you can't post at devforums.
Yeah, it sucks.