Be sure you are logged in.
Then scroll up to the top of this screen, to the menu bar.
Click on 'My Account"
After you're into your account screen, look on the left side of the screen and click on "settings and options"
Then click on "edit signature"
If it doesn't work, holler back. It works for me, but sometimes my moderator privileges confuse me when members sometimes have different paths than moderators. But if I log out to kill the moderator status, I can no longer access my account until I log back in again.