To begin you need a long, flexible gift card, Preferably one that has little to no value because you do not want to risk damaging it. If you can't find one you can also cut out a lengthy piece of soda bottle and use that instead. Once you have one of those, you can start picking locks.

First thing you need to do is slide the card as far as you can into the crack between the wall and the door frame which is the lock.
Next, you tilt the card towards the doorknob and try to push the card in more.

Finally, bend the card towards the door which will pick the lock and open the door. And that is how it is done.