implement a inventory

i start my game with a skills system tutorial and now i want implent a inventory system and quest system
in my old project i start with inventory system
the toturial i using is…aFcl1hfRb0okbz skill tutorial
iventory system…8Tpmj-iWmzqo_Q

now i want create system inventory and quest system
but i don´t know how to put in my new system