An external hard drive is a portable storage device essential for backing up files, or transferring them from one computer to another. They vary in memory size and are compatible with iMac computers. Before using your external hard drive with your iMac, it is important to properly install it. Once the installation completes, you can begin moving files to and from your storage device.
Connect your external hard drive to your power source. Insert one end of your connection cable (USB or FireWire) into the connection port on your external hard drive and connect the other end into an open USB or FireWire port on your computer. Turn on your external hard drive. You you should see your external hard drive's icon on the desktop.
Click "Finder" on the dock and double-click the "Applications" folder. Click "Utilities" and click "Disk Utility."
Select your external hard drive and click the "Partition" tab. Click the "Current volume scheme" drop-down menu and select "One (1)" partition.
Click "Option." Click on the "GUID Partition Table" or "Apple Partition Map" radio button, depending on the option you want to use. Click "OK" and select any other options you want to use. Click "Apply." This will launch the Partition Disk.
Click "Partition." The drive will be partitioned and formatted. When the process completes, specify if you want to back up your files. Close the Disk Utility.
Double-click your external hard drive's icon on the desktop to launch the drive's window. To upload files to your external hard drive, drag them from your iMac to your external hard drive's window. When you finish, close the window. To eject your external hard drive, drag it's icon from the desktop to the trash bin.