By following one of the many guide that can be found on the Internet. For example you can find lots of the at HowtoForge.com
. In the right top of the main page type Xen in the search box and browse throught the step by step guides found there. I'm sure Google will turn up a lot more. Don't expect LQ to provide you with step by step guides or howtos. If you encounter problems/questions when following a guide or howto, that's when you'll find LQ users at their best.