If you have an existing repository that was started using the terragrunt-infrastructure-modules-example repository as a starting point, follow the steps below to migrate your existing configurations to take advantage of the patterns outlined in this repository.
Look at the existing configurations in your infrastructure-live repository, and see if there are any common patterns that you can extract into a catalog.
During this step, try to take note of any common collections of terragrunt.hcl files that you repeatedly duplicate across environments, accounts, regions, etc.
Follow the steps in the terragrunt-infrastructure-live-stacks-example migration guide to start extracting common stacks out from your infrastructure-live repository into a catalog.
Take a look at the tests in test/terragrunt and use those patterns to start testing your units and stacks to confirm that they're reliably reproducible.