If you know your Booking Reference simply touch the top button.
If you made your reservation directly with British Airways and used a debit or credit card to pay for the ticket(s), you should select the second button.
Alternatively, you may identify yourself by choosing the Executive Club card button.
The fourth button will allow you to insert a passport as a form of identification. If you use this option, you will also be asked for your flight number so please have this ready.