Instructions
Turn off your Xbox 360. Move your external 500 GB hard drive near the console and connect the USB cable from it to one of the USB ports located on the front of the device. If your hard drive has its own power source, connect the cord to an open AC outlet.
Turn on the Xbox 360 and let the operating system load. When you reach the home screen, use the controller to move to the "My Xbox" menu. Move to the right until the "System Settings" menu option is highlighted and then press the "A" button to access the settings menu.
Move down to the "Memory" option and press the "A" button. You will see a list of available storage devices including your external hard drive. Highlight the hard drive and select the "A" button to select it as the secondary storage device for your Xbox, which will allow you to access its files from the "Games" and "Video" submenus.
Select the type of content that you want to move to or from the Xbox from the next menu. Once you have selected the type of content, select "Copy" to copy files, "Move" to transfer them from the hard drive to the Xbox or "Delete" to free up space on the hard drive. Select the file you want to move, delete or transfer, then hit the "A" button.