Err... you mean for displaying on an actual site?
You have to have a vhost defined for that new domain
You then will need to go into the ACP -> Settings and edit your Board URL
You will then need to update your license information in your XF customer account
That should be all that is necessary in the default XF installation.
Of course, you will also then need to go and update any outside resources (Capthca, connected accounts setups) that tie back to your old domain as an end point.