If you are in a chat room and something comes up to report look for a moderator, they will be noted with their names in red and the icons on the right of the screen in red.
The other option is to use the CC Mail feature to send the complaint to any moderator.
Take note of this part *to report a person to a mod from a chat room or through mail you MUST copy the conversation, then paste it to the mod. If you simply tell the moderator what happened, they can not do anything.
If it is a microphone offense take note of the day, the time, and who the offender is and why.
If the offense is in a forum post, every individual post has a 'report' button. Find the exact post you want to report, then on the top right corner of that post is a button labeled 'RAP'. Click it, enter a brief reason and send it.
A few of the mods names are
OnceFallen
AlaynaJ
RoboOp
1_still_waters
BillyTheKid
There are more, but these are the ones i see the most, off the top of my head.
And remember, you MUST have copy/paste of the transgression or your complaint will not be taken. They will not just take your word for it, they need evidence.