Tick anything you already have, in any order. Quests unlock once this is done.
Skyrim, Minecraft, Cities Skylines and the like have tools, wikis and people who answer questions. Modding a game nobody mods means writing the tools yourself.
Find a modding community3 things left above. Quests are real things you go and do, so they only make sense once you have what you need.
First one waiting: Install and run mods for a game