How do I get GitLab.com to push to a remote repo on a private VPS?

I created a remote Git repo on a DigitalOcean droplet and set up a post-receive hook to execute a shell script after a commit is pushed to the repo. I want to use GitLab.com’s CI to deploy to my private server. However, I can’t seem to find any documentation on how to do this with GitLab.com. I know it has a Mirror Repository feature, and I tried setting it up to push to my VPS using that, but I can’t get it to work. Maybe the syntax I’m entering into the field is wrong?

How can I set it up to do this?

Thank you