How do you book a seat reservation on british airways?

To book a seat reservation on British Airways, you can do so during the flight booking process on their website or mobile app by selecting your preferred seat before completing the purchase. If you already have a booking, you can manage your reservation online by entering your booking reference and last name, then choosing your seat from the available options. Additionally, you can call British Airways customer service for assistance with seat reservations. Note that some fare types may have restrictions on seat selection.