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)
BeardLib is only used to enable translations for other languages, and for auto-update support. BeardLib is not necessary for the main functionality of this mod.
HoldTheKey is used to enable checking when the mod is enabled. HoldTheKey is necessary for the main functionality of this mod.
When installing, please ensure that you do not have an older version of Tactical Leaning in your mods folder- delete any previous versions, if they exist.
This can happen if you are updating from older versions (2.1 or earlier), since the mod folder name has changed in v3.0 to "PD2-TacticalLeaning" (was "Tactical Leaning").