Bought a new MacBook Pro, how do I transfer the OS X Lion license to my Apple account?
I think there is a part on booting up a new mac for the first time where it asks you to register with an apple id. If you haven't done that, check in your home folder for something that is a shortcut to register with an apple id. If you already deleted that, or it isn't there, try adding a apple id in the "Accounts" section of system preferences (under your picture and name). After you register, Lion should appear under "Purchased" in the Mac App Store, which you can redownload on other machines.