GitLab Pages – Custom Domain SSL Setup Guide

gitlab

I'm trying to add TLS/SSL to my custom domain on Gitlab. Currently it says my site is available at https://yodel.co, but when I go there it says the certificate is invalid. How do I go about validating the certificate?

In the docs (also pictured) it says there are keys to add from your admin when setting up a new domain. However I'm not sure where to get these keys as I am the admin.

My Gitlab Pages
My Pages

Gitlab docs screenshot
Documentation says there's keys to add?