First you must purchase and register your URL from a provider, such as GoDaddy.com, or Google. Ensure wherever you choose to purchase your domain allows URL forwarding.
Forwarding has to be set up from the URL provider's end. You will need to log into said account and search for URL forwarding instructions. They should have help documentation to walk you through the process.
Once set up, anyone who types in your custom URL to their browser or clicks on a link with that URL, will automatically be redirected to your PlayyOn site. This is great for marketing purposes or for easily sharing your URL with players, parents and fans.
PlayyOn does not yet sell ULRs or support completely replacing your PlayyOn URL as of the date this article is written.