To format a flash drive on a Mac, plug in the drive and open the 'Applications' folder, the 'Utilities' folder and then 'Disk Utility.' Your flash drive should be listed in the left menu. Step 1 To start with, connect USB drive that you want to format to your Mac. Step 2 Then, select “Applications”” Utilities”. Next, open the Disk Utility. Step 3 Now, you need to choose the USB drive from the si..