How do I add an item my inventory via an in-game store?

I am in the process of creating an in-game shop (NOT an in-app purchase, but more of a trader shop). I have created a basic inventory system that works on pick up items already. For the store, I have created five buttons to represent the five items for sale. If you click any of the buttons, a new box of options appears, asking you to confirm or cancel purchase. So, my question is, how to do I get the confirm button to interact with my inventory system to add the purchased item to my inventory?

NOTE: the store and inventory system are both done through UMG (and I used the simple inventory system on Youtube provided by Unreal Engine to set up the inventory).

You need to use gamestate blueprint to store your varibles so when match ends or next level it dosnt lose it stuff… and then basic UMG menu same thing as health or ammo logic… im newish so beyond that id like to know aswell… ie use structs functions etc instead of all the code in one blueprint…