I already have a website configured on my x10 domain, but want to replace that domain with my custom one. How would I do that? i.e what settings would I pick (parked, etc.) and how would I transfer everything over? Is there an easier way? Thanks.
You should pick parked. Before doing so you would need to update the custom domain to use our name servers, they are ns1.x10hosting.com and ns2.x10hosting.com.
Once the domain is properly added to your account you would likely need to go into the admin panel of the script you use and update the configuration to use the custom domain rather then the x10 domain (otherwise it would probably just redirect to the x10 domain when visiting the site). How that is done depends on the script used.