I write short stories.

I recommend just sitting down and starting to write. A novel is a tall order, and writing is one of those interests that gives back what you put into it. Worrying about how good it is (especially when it's a gift) before you have any content to think about changing is just going to keep you at the starting line forever.

Worst case scenario, there are a few chapters you don't want to keep and a few scenes that need to be earlier or later. I don't think anyone's first story on their first try has been stunning.

Some things that might help are to pick out a good word processor if you don't already have one and to write a quick outline. Word is a good default, and I sometimes use Jarte because it's minimal and never, ever disrupts me or my settings for any reason. I don't usually write more than a couple paragraphs on the structure, key points, and surprises I have in mind and stay open to last-minute ideas.