Create an app for the Google Mail and Google Drive application.
Before You Begin
Make a note of the application client ID of your service account that you observed when you delegated the domain-wide authority to the service account.
From the navigation pane, click Protect > Applications > G Suite.
The G Suite apps page appears.
Click Add app.
The Add app dialog box appears.
In the Application type box, select Google Mail or Google Drive.
In the Connection details section, enter the following information:
Email ID: The email ID of the super admin.
Application client ID: The client ID of your Google service account.
Application email address: The email ID of your Google service account.
In the General section, enter the following information:
App name: The name for the app.
Proxy: Select the server where you installed the Cloud Apps package.
Application private key file path: Type or browse to the location of the PKCS12 key that you obtained when you created a service account.
Plan: Select a server plan.