Formatting your drive for a Mac
STEP 1: Open Disk Utility like this:

Click Finder.

Click Applications.

Click Utilities.

Click Disk Utility.

STEP 2: Select the drive you want to format. Be sure it’s the correct drive.

STEP 3: Go to the Partition tab.

STEP 4: Click on the Current Volume Scheme drop-down menu and select One (1) partition.

STEP 5: Click Options. From the Partition Schemes provided:

Click on the GUID Partition Table radio button.
--OR--
Click on the Apple Partition Map radio button.
STEP 6: Click OK. Select other options as desired (e.g., Volume Name, Format, etc).

STEP 7: Click Apply. The Partition Disk screen opens.

STEP 8: Click Partition. At this point, the volume dismounts from the desktop and the drive is partitioned and formatted.
Note: When Volumes are created, Time Machine may open, asking if you would like to use the volume for backups. Click Cancel to proceed.

STEP 9: When finished, select the Disk Utility from the Apple Menu and choose Quit Disk Utility.