Please follow the steps below to format hard drive:
1. Double left-click on your Internal Mac drive and choose Applications -> Utilities and double-click on Disk Utilities.
2. In the far left pane, choose the drive that you want to partition and format. Typically there are two listings for each drive unless you have more than one partition on a particular drive. Choose the drive listing that is farthest to the left for the drive that you want to format. It is usually directly above the name of the drive.
3. Click the Options button and choose Apple Partition Map. Then click on Ok.
Note: If you cannot choose Options because it is grayed out, click on the Current dropdown menu and click on 1 partition. This should make the Options button useable again. Also, if you receive an error that the drive cannot be unmounted, shut down the Mac, unplug the drive from the Mac, turn you Mac back on and when it is fully loaded to the desktop, connect the drive and try again from Step 1.
4. Change the Format to Mac OS Extended (Journaled). You can also give the drive a name by typing it into the Name box. When you are done, click on Partition.
5. A box will come up letting you know that formatting and partitioning the drive will erase all of the information that is on the drive. If you don’t need any of the information on the drive, then click on Partition.
6. The drive is now formatting and you will see a status bar at the bottom that says Creating Partition Map. When it is done, this bar will go away and the drive should now show up on your desktop.