If you haven't got your boarding passes but in online check-in you appear as checked in, you can request a duplicate pass from your computer or phone. Log in with your details to online check-in and at the bottom where it says 'What do you want to do?', select 'Print boarding passes'. You can then select the boarding pass format and how you want to receive it.
Remember, if you forget your boarding passes you can either get them at the check-in machines or request a copy at the check-in desks.