You can upgrade to OS X El Capitan from OS X Snow Leopard or later on any of the following Mac models. Your Mac also needs at least 2GB of memory and 8.8GB of available storage space. Option (⌥) or Alt: Start up to, which allows you to choose other available startup disks or volumes. Command (⌘)-R: Start up from the built-in system. Keep holding until the described behavior occurs.
To use any of these key combinations, press and hold the keys immediately after pressing the power button to, or after your Mac begins to restart.
Mac mini introduced in early 2009 or later MacBook Pro introduced in mid 2007 or later MacBook Air introduced in late 2008 or later MacBook introduced in 2009 or later, plus MacBook (13-inch, Aluminium, Late 2008) Or use Option-Command-R or Shift-Option-Command-R to start up from macOS Recovery over the Internet., depending on the key combination you use while starting up. If your Mac is using a, you’re prompted to enter the password. Mac Pro introduced in early 2008 or later
