Click on Membership
Click on Reset Cookie
You'll get a screen that says "Login"
Type your code name (this has to be exact) into the block labeled "CodeName" and click submit
You'll get a screen with a block labeled "CodeName" which is filled in, and a block labeled "Password" which isn't.
Type your password in and hit "Submit Query"
Do not back up to get to the forum. Click whatever it is you click to get there in the first place. If this doesn't help, let us know at which point something didn't do what you expected, and we'll take it from there.