The Function (or Fn) key is used by HP and other computer manufacturers on compact keyboards (such as laptop keyboards). The Fn key works in the same manner as the Shift key, it must be pressed and held as another key is pressed. The purpose of the Function key is to combine two keys together and thus, save space on the keyboard. It is used for this same purpose by all computer and keyboard manufacturers.
Locate the Function (Fn) key on your keyboard. The most likely location for this key is at the left bottom side next to the Ctrl key. The letters "Fn" will probably be shaded a different color than the rest of the keyboard, a common color being blue.
Locate the combined Function keys on your keyboard. The Function keys will most likely be combined with the F1 through F12 keys and they will be shaded the same color as the Fn key.
Press and hold the Fn key and at the same time press and release one of the combined Function keys. The Function command will now take place instead of the default command.