How to create a functional mod?

Hi, I've been wanting to become a Sims 4 modder for a few years now. I've done basics things like creating custom wallpapers/floor etc. Last year I came up with an idea that I want to make a mod that will have to require you to have dog/cat food in order to fill pet bowls and not just fill the bowls for simoleons. So example SimRealist Home & Land Co mod has someting where you can add detergent from the "Dabra" object in buy mode. There is a object (I don't know the name) like a deco object of pet food. How can I make that functional like not being able to fill the pet bowl food without the bag of pet food, also to require water for the pets aswell because in real life cats and dogs need water too. I want to try this with cc pet food (if I have the permission from the owner to) but first I want to learn how to do it with objects that are already in game.