Step 1. Go to your domain registrar and set the name servers to ours, which are: ns1.x10hosting.com and ns2.x10hosting.com
Step 2. Login to your account here and add the domain as either parked (alias of the main domain) or addon domain (separate site).
Please note that there may be a delay before you can actually execute step 2, the new configuration for your domain needs to propagate, often very quick but can take anywhere from a few minutes to a couple days (rare case).
At this time we do not allow having a custom domain as the main domain on a free hosting account.