It should send a link to the email you registered to the forum with. From the link they email you can just retype a new password. Had to do this last night actually. No need for the old password.
When you type in your email and password on the forum it will say forgot next to the password blank. Click that. A new box will open where you type in the email you registered with. Then it will email you a link. It may be in your junk email like mine was so check there. Once you get the email follow the links to reset the password