Drop off the mail. Then get to the chopper! Use A and D to jump left and right. Tap it to jump a short distance, or hold and release to jump farther. You can also jump off walls! 

The catch in Slippery Delivery is that once you start moving, you won't stop until you crash into something or slide off. Don't let yourself slide off a cliff or into dangerous objects!

If you want an even tougher challenge, try to collect all the floating envelopes in each level.