Once it is installed, just boot up from the install disks and the installer will walk you through initializing the drive.
A far easier way would have been to clone your internal drive to a USB or FW drive using SuperDuper, then cloning it back. That way all of your programs and settings would be exactly as they were before the swap.
I did that with my iMac when I upgraded it from the 160GB drive to the 320GB unit that I now use.