*Note: I've been really busy recently, so I will not be able to give critiques. OCD isn't going down, though, but you guys just won't see much of me in the comments. I'll probably be appearing more after April 24th.*
As for how this goes, you post a work of yours, finished or WIP (aka work in process, for those who are new to abbreviations), and then others give you critiques on your work. I do not mind if you post the occasional non-HM picture or piece of writing. Just make sure that you only post pictures that are your own design and not any that copyrighted or based off of copyrighted characters.
Also, if you post a work, it is highly recommended that you also give someone else a critique.