Hi,
When you want to change the welcome text within your homepage you need to edit the language variable related to the welcome text. Just go to: admin> languages, choose your language from the dropdown box and use the "filter" box to search for: txt_welcome and edit that content
If you want to change the layout of your homepage then you have do change some templates and/or CSS files.
A good start can be found here:
http://forum.x-cart.com/showthread.php?t=21529
Cheers,