migration after a machine has been used?

[Racer X]

I recently got a used 2009 MBP here, and want to migrate everything from my 2007 MBP, but the 2009 has already been run.

I know there is a way to run migration assistant after the fact, but I have no idea how.

The 2007 will become a media server with a buttload of drives plugged in to the plethora of ports these older machines have. That and a USB 3 hub.