Basically, Shopify private apps live here: https://myshopify.com/admin/apps/private
To create an app, you’d go to https://myshopify.com/admin/apps/private/new, get it a name (use something descriptive like Automatic Customer Tag by 99rabbits), supply it with our email firstname.lastname@example.org and hit ‘Save app’.
Then you’ll be presented with apps’ API credentials. You need to copy all of them and hand over to us.
Should look like this:
NB! You’ll be able to disable the app and completely turn off our API access whenever you like.