After downloading the mod, use a program such as 7zip or WinRAR to extract the main folder of the mod.
Drop that folder into the mods folder which is supposed to be in the game's installation folder (don't know where that is? click here)
HoldTheKey is required to use the Modifiers feature. Please only enable Keybind Modifiers if you have HoldTheKey installed. BeardLib is optional, and is only used for auto-updates.