Store Weapons, Armor and quest items inside your Inventory.
To get an asset to go in your Inventory you need to apply the 'Collectable' Component to it. While playing your game you can access your Inventory by press 'I' on the Keyboard. Everything you have collected in the game will be stored here.
You can drag your weapons and armor to the correct slot on the right to equip it and gain in power.
Items that cannot be equipped go into the Quest Items tab.