So, at check-in, not at the gate. The PP I quoted said at the gate which is no more than maybe half an hour before boarding (depending on when the gate agents get there).I don't think you have to actually go up to the customer service agent. I think the app assigns it and updates your barding pass in the app. I think you only have to approach the actual agent if there is an issue. If you don't check in online before a certain amount of time before the flight, you would have to check in with the customer service agent. I am not sure when you ahve to do it by but you can do it as early as 24 hours before your flight.