First detach the mattress from the hooks. Fold up the mattress and put it in the storage bag. Fold in one leg at a time and be careful to pull out the leg before you fold it. Fold up the crib in the middle and put the crib in the bag, between the mattress pad. You can find a tutorial here.
Tip: We’ve found that flipping the frame upside down and pulling the legs up is the easiest way to make sure the legs fold properly. We made a tutorial you can find here to help you out.