I'm going to assume when you say "doing stuff", you're referring to buying/selling/trading since this is posted in the Bazaar section;
Make a post and select what category the post is for (Characters/Plat/Services/etc...).
Then select the game you're wanting to buy/sell for via the Prefix (EQ/EQ2/Project99/etc....).
If you're selling a character/account you'll want to fill out the the level/class/race.
Post some details of what you're offering and/or what you're looking for.
Ok thank you I will figure it out a little more before I decide to do anything here.
Typically people leave feedback for each other after the transaction. Scammers get banned by mods. If something seems too good to be true, it probably is. If you're new, don't take too much offense to people doubting you as there have been an influx of sketchy posts lately.
If you need more information, post some more specific questions we'll help you out.