5
Wait a minute -- you said you had a phpMyAdmin control panel. Do you mean you've got a hosting setup that provides a phpMyAdmin control panel, or just that you've downloaded the files? If you've got a phpMyAdmin control panel from your hosting company, then you've got a database from them, too. You just need to make sure you're using the right username and password, and pointing to the right place.
Or if your host has some special procedure for creating a database, you may have to fill out a form or something. Or, if you're managing your server yourself and you don't have a database server at all, you still have to install MySQL
I'd go with the latest production release, though XOOPS will run just fine with 3.23.