Your Seagate Backup Plus Will Be On Your Desktop. Check The Scheme Says GUID Partition Map. The Next Window Is Where You Set Up How You Would Like Your Seagate Backup Plus Formatted. Then Take A Look At The Top Of The Disk Utility Window And Click On Erase. The Left Side Of The Disk Utility Window Shows You All The Drives You Have Connected To Your Mac. Look For The Backup Plus External Hard Drive Icon On Your Desktop. How To Format Your Seagate Backup Plus For Mac.