There is 2 levels of names at the message board:
1) Account name that is associated with your password and is used for identification
2) Displayed name that ANY member can change
To change your displayed name:
- go to your profile, click "Edit Settings"
- chose tab "Displayed name"
- enter your new nickname and save it
As you see from the screenshot above, you can do it only 2 times a month.
BTW: I an posting this with 1 post and as "Member"