It should be the one you use to log into phpMyAdmin, if you continue to get the access denied error, you should contact your host, they will be able to give you more information than I on the subject of the user name and password to use.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.