Hi I’m new here too.
I don’t know if this will help the OP (or anyone else) but I had similar difficulties setting up my first install of MODx evolution on Wampserver today.
I had no idea what information I was meant to provide in the Database login name and Database password fields.
Mary advised "the information you enter here is generally your login information for your server" which didn’t help me much, being a WAMP newb as well as a MODx newb.
Anyway, I managed to figure out that the login information for the default installation of Wampserver 2.0 is login ID "root" and no password. This information is visible if you browse phpMyAdmin from the Wampserver manager icon in your Windows tray, and click on "Privileges".
Entering this information on the MODx install page allowed my installation to continue and MODx then set up its own database.
HTH someone.