OS X El Capitan: Change modifier keys
You can change the behavior of the following modifier keys: Caps Lock, Control, Option, and Command. This is useful if you’re familiar with a keyboard layout different from your current keyboard.
For example, the Control key on UNIX and Sun computer keyboards is located where the Caps Lock key is located on Apple keyboards. For experienced touch typists, this can be awkward. Changing the behavior of the Caps Lock key to Control solves this problem.
Choose Apple menu > System Preferences, then click Keyboard.
Click Keyboard, then click Modifier Keys.
Click the pop-up menu for each modifier key you want to change, then choose an action.
To return the keys to their original settings, click Restore Defaults.