How to format your drive in macOS 10.11 and above
Note: Reformatting the drive will erase all data on the drive, so you should copy any data you want off the drive prior to formatting.
The following is based on the latest version of macOS.
1. Open Disk Utility
Applications > Utilities > Disk Utilities
2. Select the Seagate drive on the left.
Note: If you don’t see the drive listed then change the view in disk utility. The view button is in the upper left-hand side, change to show all devices. This feature was introduced in macOS 10.13 and not available in 10.11 or 10.12.
3. Select Erase which opens the following window.
4. Rename the drive
5. Select OS X Extended (Journaled) for Format
6. Select GUID Partition Map for Scheme
Warning: Formatting the drive will erase all data on the drive, so you should copy any data you want off the drive prior to formatting.
7. Select Erase again.
8. Disk Utility will start formatting the drive.
9. Once complete, click done.