Define Shortcut key in Unity3d ?

I found shortcut keys in Unity Preferences window,but there are about ten shortcut keys for

user to define,So How can I define “Play” or “Pause” shortcut keys in unity?

I think that’s useful for me not to click mouse to play the game every time.: )

If you’re on OS X, use the system keyboard preferences to add keyboard shortcuts to any app. If you’re on Windows, I believe there’s some 3rd-party utility that does something similar.