Using PayPal Express with Commerce?
The example templates work with PayPal express out of the box, there is nothing special you need to do. 

You can only add PayPal Express as a Payment method when you have bought and registered Craft Commerce. 

Paypal Express is an 'offsite' gateway, and it uses the exact same form as the dummy payment form but posts the form without the credit card inputs - that form then redirects you to PayPal.