You can do that, by going through Disk Utility.
*To get to Disk Utility:
• From your desktop,
•Click anywhere on a blank space on your desktop. Now you should see Finder
listed near the Apple menu icon.
• From the Finder menu, click on Go, then Utilities
drop-down menu. This will take you to your Utilities
• Locate and launch the Disk Utility application
Now from here once you connect your hard drive to your Mac, Disk Utility will display the drive on left side window in the application.
Next, click on the Erase tab and select either MS-DOS or Mac OS X Extended proceed from there.
• Now keep in mind as well, you can also select to partition the hard drive if you so
desire before you set to reformat the hard drive.
Let me know if this helps.
If you have any more questions, regarding your technical issue, please feel free to reply to this post as I am always ready to assist. Thank you!