How to add an external domain to WordPress MU (Multisite)

If you have ever wanted to manage multiple top level domains from a single WordPress MU Multisite installation, here is how you create new domains.

Pre-requisites:

1. WordPress installed
2. Multisite setup installed with subdomains selected.
3. Domain Mapping Plugin installed and configured

These steps are in order in the gallery, you should follow the step in each image, there were no skipped screens so you should see every screen that you see here.