I don't have administrator access for my MacBook Air and I need the username and password to be able to administer my laptop.
Boot off the recovery partition, open up terminal, and type
That should bring up a dialog that will allow you to change your password If, for some reason, the default account is not set as admin, you will need to boot into Single User Mode (⌘-S when starting up) and type:
mount -uw /
This makes the file system writeable, and then removes the file that tells OS X that you've setup the system. Hit Ctrl-D to continue your boot and you should get the "Welcome to Macintosh" startup and you will be able to setup a NEW account (make sure it is a new account). This account will be an admin account.