To get started select
Tasks settings > Synchronization > Google Tasks > Add account
Grant the contacts permission
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.