Ivano you must read this https://developer.paypal.com/docs/classic/mobile/gs_MPL/ and open Sandbox accounts: https://developer.paypal.com/webapps/developer/applications/accounts
Ater you have 2 address one to buy the other for receive money ( SandBox ) so you can try example that you have in #1.
Ater you have 2 address one to buy the other for receive money ( SandBox ) so you can try example that you have in #1.