The Settings tab is only accessible via the Web App.

View and manage your account settings

The first section is your OneList account details.
The other sections are your source system account settings in OneList. These sections allows you to setup and maintain the source system user id associated to your OneList account.
If the "Not Applicable" is selected then OneList will not process any of your task from that source system.
If the "Not Applicable" is not selected then OneList may prompt you to sign in to the source system and complete the source system account set up process.

Don't forget to click the Save button to commit your changes.

Maintain synchronization settings

You can activate and deactivate the notification channels. Click the Save button to commit your change.
Use the "Sync Now" button to update your tasks e.g. when the expected layout change is not reflected in your tasks.

Choose how tasks are displayed in the Web App Inbox. If not specified then the Category View mode is used.