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.