Installation (for A-10C 2, instead remove _2 from end of path for A-10C):
Beta: Right click and extract the zip to C:\Users\YOUR USERNAME\Saved Games\DCS.openbeta\Kneeboard\A-10C_2
Main Branch: Right click and extract the zip to C:\Users\YOUR USERNAME\Saved Games\DCS\Kneeboard\A-10C_2