I have just written a hub on how to write the first draft of a novel, but I don't think I'm allowed to post you the link! But you can read it if you like. It doesn't tell you how to come up with the ideas, because I'm saving that for a different hub.
Basically, though, I start with an idea and just write down everything that pops into my head to do with that idea. A character might emerge and I then expand on that character and find them a purpose, a quest, a task or something. You can't have a story without a purpose, as far as I'm aware - your protagonist needs to have something they're working towards, no matter which genre you choose to work in. You can introduce family and friends whenever you like - and that can be lots of fun too, watching your characters interact with each other (they very rarely behave as you want them to, and you end up having to edit conversations A LOT!).
The main bit of advice I can give right at the start is to just allow your mind to wander, and don't try to force things to go in certain directions - that part can come later when you've got a story to work with. Initially you just need to play around with ideas and see what comes out of it. It can be surprising, and you may find things in your head that you never would have expected to be there!
The first stage is all about having fun really, and playing. Enjoy.