Welcome to X-Cart! Please start by reading the forum rules, and posting your X-Cart version in your signature (Edit profile, enter version, enter password, click the 'Always attach my signature:' box, save):
http://forum.x-cart.com/viewtopic.php?t=6489
You can add any kind of html you want to the X-Cart templates. If you want to add an html menu with rollovers, you'll need to put some JavaScript in the <head> of your site (found on home.tpl) and then put the actual menu code in head.tpl.