To add your own root custom domain (not a subdomain) on PixelMe, please follow these steps:
On your domain provider, select your domain and go on the DNS part.
Point your domain to our servers by creating (or editing) a A Record pointing to our IP 18.104.22.168
Wait a few hours during the DNS propagation.
When your domain redirects to getpixelme.com, that means it works!
Add your domain on PixelMe by going to your Link Manager settings, Custom Domains and Add a custom domain.
If you are looking to add a Sub Domain, please read this article.