I am trying to complete the last step of the ssh key authentication process but I am not sure what my GitLab instance URL is. Just so I am not confusing anyone here is the copy and pasted snippet of what I am trying to figure out. Thank you.
If you have installed your own server, then it is the hostname and domain name of your server. This is exactly what would have been put in the external_url in gitlab.rb. So, as from the documentation you replace gitlab.example.com with whatever you put in external_url.
So for an example, I create a server called mygitserver and use mydomain.com as the domain. I put in external_url mygitserver.mydomain.com in gitlab.rb, so my instance url is that value. Then as per the docs, once the SSH key has been added to your user profile, the SSH command is:
ssh -T git@mygitserver.mydomain.com
your instance url is also used in the web browser as https://mygitserver.mydomain.com