Custom domains

Custom domains can be added easily directly on the link creation page.
Add to 404 error page of your site
To configure a custom domain, use the following HTML script tag on the 404 error page of the domain. If you don't have a website attached to the domain, Netlify is a good place to deploy and add the HTML file with the below script.
If using Netlify, be sure your uploaded file name is 404.html. Otherwise, it wont work.
<script src=""></script>
Once you added the script, you should be good to go.