Adding a working inventory

Hello! I decided that the inventory I was simply insufficient (and barely functional) and that it should be improved, but I am unsure on how to go about starting such as task. I would like it to be so that when the player gets an item (either via chest or shop) it places it one of the inventory slots shown in the image below. Currently the inventory is an external layout and the code for it is an external event, which I feel like is correct! I assume I’d have to give an item a variable or tag of some sort? Then if the player buys a shop item or picks up something from a chest, set it to true and show it in an inventory slot? Just not sure completely how to go about that.