If you want your old AOL account to work again, you must first verify that your browsers saved your last password. Modern browsers offer to remember the password and just check if you have previously saved the password or not.
If you still do not know the password and remember only your username. In that case, you should contact AOL Customer Service and they will take you through the process to reactivate AOL Account. It is listed on their website that if you want to restore your old account you should give them an AOL's phone number and they will be happy to talk to you through the recovery process.
