The "F-Lock" key on a Windows keyboard is also called the "function lock." This key, when enabled, allows you to use the secondary functions of many of the keys on your keyboard. This key is not something that is permanently enabled on most keyboards. Typically, you must hold the key down in order to use the secondary function of your desired keyboard key. The secondary functions of keys are always printed on the keys themselves.
Locate the "function lock" key on your computer's keyboard. Typically, this key is located in the lower-left corner of the keyboard, but depending on the model it may be in a different location.
Press and hold the "Function Lock" key to enable the function keys on your computer.
Press one of the "Function" keys on your keyboard to enable that key's primary or secondary function (depending on the specific nature of the key you're pressing).