Need help making GUI text on off when you press a key

Unity Engine
1

So I am making a horror game called Haunt. I want it to say whenever you start up the game “Press F to turn on your flashlight.”

I already have all of the flashlight scripts, models, etc. made, I just need to get a script that makes it so that when you press F and turn on your flashlight, the text fades away.

ty all people who answer.

2

to detect Input: http://docs.unity3d.com/ScriptReference/Input.html
to enable/disable a light see http://docs.unity3d.com/ScriptReference/Light.html