Just start! Maybe in Scrivener. 😉 But you’ll probably quickly develop many questions about how to get better at it, and the business side of things, and why you stare at the wall so much. (Or is that just me?) I recommend finding a local or online writing group, or attending a regional or national conference. There’s nothing like finding other people who stare at the wall, hear or see characters, and get story ideas in the weirdest places. There are dozens of genre-specific and general writing groups out there. Try a web search or your local library. Read in your genre, read books on writing, check out writing magazines and websites like WriterUnboxed.com. But most of all, write.