Automatic check-in allows you to check in and select your favorite area before the airline check-in window opens. This way, you don't have to worry about the availability of your desired seat! This is part of the premium subscription, but you can try it for free for 14 days (access to the free trial period is in the annual subscription).
For iOS, go to Profile > Try Subscription; For Android: Profile > Settings > Manage Subscription.
To request automatic check-in in the Boarding Pass widget for an upcoming flight, click Auto check-in, then go through the steps to fill in the required information, and then click Submit.
If you want to add passengers for automatic check-in, click the "+" button before you click Submit, fill in their information and preferences, and then submit the request.