This is probably one of the most common questions emailed to site support. How do I change my "badge" under my name?
This short video tutorial walks you through that process, and explains the info you see by your username when you post.
You need to go to your UserCP and click on PERMISSION GROUPS to get things going.
If there's other topics you'd like to see video tutorials on, PM me or post the suggestions in the Site Support forum, and I'll try to make that happen.