Remove two T6 Torx screws from each side of the hard drive (four screws total).

You'll need to transfer these screws to your new hard drive if you're changing drives.

If desired, peel the pull tab off your old hard drive and transfer it to the side of your new drive.

If you are installing a new hard drive, we have an OS X install guide to get you up and running. Many recent Macs may be able to use OS X Internet Recovery.