Adding a Google Task account

To get started tap on ☰ > Settings > Synchronization > Add account > Google Tasks

Grant the contacts permission (Android 6 + 7 only)

Tasks requires the contacts permission on versions of Android prior to 8.0. This permission is needed to access the Google accounts registered on your device

Choose an account

Select the Google account that you would like to synchronize with. A subscription is required to synchronize with two or more Google accounts

Grant OAuth 2.0 access

Tasks requires permission to use the Google Task web API with your account. If you no longer use Google Task synchronization you may revoke this permission by visiting your Google security settings.

Please note: Tasks.org will be flagged in your Google Security Checkup because I am unverified developer. Unfortunately it costs approximately $15,000-75,000 USD to get verified, so this situation is unlikely to change