Using it is very simple. Just copy over the headers, then the code wherever u like, prefereably create a blank c++ class and do it.
Each step can be done in both c++ and blueprints:
INSTRUCTIONS
Step 1: Constuct object on beginplay
Step 2: Call the recoil tick from the created object on event tick/tick function.
Step 3: Define a recoil curve for your weapons and set it inside the object as well.
Step 4: Call RecoilStart function when the player starts shooting.
Step 5: Call RecoilStop function when the player stops shooting.
Thats pretty much it.
If anything goes wrong, you can ask it on my discord server: https://discord.gg/FBz3amt