Instructions
Connect your external hard drive to the PlayStation 3 by using the bundled USB connector cord (that came with the drive) and plugging it into the console's USB port (on the bottom of the console.)
Power on the PlayStation 3 and sign in to the master account. Once the XMB has loaded, a notification will pop up on the right side of the screen informing you that a mass storage device has been detected.
Navigate to the left side of your XMB. Under the "Pictures" "Music" and "Videos" tabs, a small icon will appear with your hard drive's name on it. You can now browse the contents of your hard drive by selecting the type of media you want to view and then pressing the "X" button.