Build Validation template for all repos

I'm new to Azure pipelines so this might be a silly question, but I was hoping to create a pipeline template that will run some basic checks that would be applied as a build validation.

Here's what I am trying, but again, new to this so it may not make sense.

Create a repo with pipeline template, let's call it ado-templates/basic-checks.yml

On a separate repo and branch, set a Build Validation policy to require the running of ado-templates/basic-checks.yaml.

When that branch gets a PR the pipeline runs, but it only checks out the template repo. How can I get it to dynamically pull in the repo with the build validation policy and run the basic-checks.yml pipeline against it?