Do you want to update MAMP and worry to loose your data like your localhost websites and database? Read along, I updated my MAMP a few days ago, using Yosemite Mac OS. It should work with newest Mac OS version.
This post is for the free version users. For pro version, you can visit their official documentation.
Actually, I used MAMP server quite a long time ago, basically since I knew how to install WordPress locally on a Mac OS X.