Make sure your project you just created is selected in the Projects menu just right of ‘Google APIs.’ Then click on the main menu:
Select IAM & admin > Service accounts:
Create a service account:
Make sure you check on the radio button for your json private key. You can leave the Role unspecified.
Click Create and the json will download. Store it in a secure place, as you will need it later in the setup.
Next Step: Enable the APIs