If you have upgraded to OS X 10.11, go to our new guide for El Capitan.
Before you can use your new SSD with your Mac, you have to initialize and partition it.
- Connect the SSD via USB adapter or other external connection method. When the SSD is noticed by the Mac, you will see a message telling you that the drive cannot be read by this computer. In this message, click the button Initialize.
- The Crucial SSD will be listed in Disk Utility. Highlight the SSD and click the Partition tab.
- Click on Options and verify that it's set to "GUID Partition Table".
- Select Partition 1 if you want to use the entire SSD as a single partition, and give it a suitable name.
- Verify that the selected format has defaulted to "Mac OS Ex tended (Journaled)".
- Select Partition. The drive will now be partitioned and formatted.
- When the Disk Utility is done, close it.
The SSD should now be visible on your desktop with the new name you gave it.