Here ya go!
http://s26.postimg.org/xfspthvlh/Power_UP.jpg
Basically whats happening is when you press a button, The Spacebar in this example. It checks to see if a Bool variable called Boost Ready is true or false. If true it adds the power up. After the power up is added it sets the value of the Bool to false. This way it can’t be triggered again. Then a delay is set. After the delay the Bool is then changed back to true, now the power up can be triggered again. Hope this helps.