How to apply Inventory System to Player looks (What player is holding)

So I am making a top down game for pc, it is like a realistic apocalypse survival adventure game, I haven’t made the inventory system yet and I want it to be where you basically find weapons around the world and can then pick them up and use them. I need a good turtorial series or forums telling me how. Please tell me where to look for a good inventory system.
Then I want to apply the inventory system to my character looks. I have been debating on what to do for my charcter for a while and have decided to do no legs showing so not really 2d but a 3D character down to the shoulders which will then show what item my character is holding. How do I make a simple way so when a item is selected in my inventory system my character then holds it.

I have the meshes already for weapons and grendades btw

Thanks for help hopefully someone will spend the bit of time to help me (:

Bump*****

2nd bump need answer soon plz (:

No much helping here just lots of trial errors and lots of hard work, I did it and many others did the same before me. Here is the exact tutorial you want: Tutorial? Good luck.

Ok…

Well I might as well climb into a hole then and die… I have no clue where to even start

Dude, you start from the tutorial…