For branded apps we require you to provide an API key for use with Google Maps services, i.e. customer address lookups for billing and delivery addresses, and showing your closest store to the user in case you have multiple stores.
Google provide their own guide here for getting an API Key:
Once you have obtained a key, you will also need to enable the following APIs:
You should just be able to visit each of these pages and click Enable:
Finally, make sure that billing is enabled:
In most cases, the free tier is sufficient and you will never be charged, but billing still needs to be enabled.
When this is completed, send your API key to us: firstname.lastname@example.org