Make sure to first have SuperBLT installed. Click the link in the dependency list.
Optional video tutorial for installing SuperBLT, BeardLib, and mod_overrides mods: https://youtu.be/rin_sjSJIkg
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)
After download, Unzip file with 7zip or WinRAR.
Move Skill Tree Background Restoration into mods
Choose 1 to use and move the one of your choice to your mod_overrides folder (don't put all three versions in there might crash your game or might not work)