Using Route53 as external DNS (Kubernetes install)

I am stumped. I am trying to install Gitlab on AWS. The basic install went fine, moving from minio to S3 eventually went fine as well. But now I am completely stuck. I would like to use External DNS in order to automatically update my DNS records in Route53. How to achieve this a complete mystery to me.

I have found this docs page. Basically, it states to add the following to my LoadBalancer service:

Where exactly in the config hierarchy does this snippet go? And is that all that is needed to activate external DNS?

If not, can somebody point me in the right direction? Is there more documentation available specifically for Gitlab?

Regards Emiel