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)
Notes from the mod author:
BeardLib is only used for auto-updates and non-English localization, and is optional. Unless BeardLib is installed, you will not be able to use any non-English localization for this mod or update it through the BeardLib mod update menu.
TdlQ's QuickKeyboardInput is only used to allow typing the screenshot save path with an in-game menu, and is optional. Unless QuickKeyboardInput is installed, you will not be able to edit the screenshot save path while in-game. Note that you can still edit this path manually by directly editing the mod's settings json file.
Neither of these mods is required for the main functionality of this mod (taking screenshots).