Changing Models in a Minecraft Resource pack

As I have said in previous questions, I make resource packs for Minecraft. I am working on a new one, and after seeing others, I would like to change the shape, to make them 3D (e.g. Sword is not flat, Trees have indentations for the bark). I know you need to use the models file of a resource pack, but when I go in to change it, I don't understand what to do. Thanks!

Solution 1:

Actually, you can edit .json files. You just need to use something like Notepad++ and know how codes work. When you "save" I'm pretty sure it stays a .json

Or, if you want to "save as", you have to change to "all files" and rename it with .json If you don't do that, the file will just save as a .txt

Your computer should understand what you're doing and make it a .json This is for windows though, I'm not sure how Mac works.