Here's some quick pictures to show how to add an mSATA SSD to a 2012 or early-2013 MacBook Pro Retina (13 or 15 inch model) This is for the data transfer. You don't need this part if you are just going to install the new SSD and re-install OS X from scratch or a backup. Clockwise from the top, we have a USB 3.0 SATA enclosure, mSATA SSD drive, mSATA adapter for rMBP, and a mSATA to SATA adapter. When you connect this drive to your Mac you may have to initialize it I'm using the free trial of Carbon Copy Cloner to copy my existing drive over to the new one. It only takes about 5 minutes to do. It may take longer or go even faster depending on how much data you have. Remove the back cover of your MacBook Pro and you'll see the SSD Instal the new mSATA SSD into the adapter, and then install that into the place where the old SSD was Re-install the bottom cover of your MacBook Pro and you're ready to go. Run the 'sudo trimforce enable' command from a Terminal when you boot back up to enable TRIM.