gitlab kubernernetes integration: configuring the installed runner
Installing kubernetes integration on gitlab
In Admin Area -&gt; Overview -&gt; Runners, the instructions they give are:

Install GitLab Runner
Specify the following URL during the Runner setup: https://&lt;your gitlab hostname&gt;/
Use the following registration token during setup: &lt;insert-token-here&gt;
Start the Runner!

I'm on version 13.13.0 but I don't remember the instructions changing from version 12.x.x.
Project specific runners
As for your question regarding configuration, I'm a little bit confused if you're looking for something beyond those instructions. If you want to set up a runner specific to a project, you can go to a project then navigate to Settings -&gt; CI/CD -&gt; Runners -&gt; Specific Runners. There, there are more instructions on setting up project-specific runners.
Further configuring the runner
EDIT: The executor entirely depends on how the runner itself is installed. If it's installed on a kubernetes cluster, then it must be the kubernetes executor. That will affect your pipeline. I think you can create another one if you install another one with the runner chart. You can also use Helm Tiller.