For a second I thought I had written this question because it is literally my situation 4 months ago. Most other answers have given you a bit to work with but I think they are a little too narrow. The best piece of advice I have seen here is to just start writing. I have a dropbox account linked to all of my devices so the moment I get an idea I can open a new Text doc and title it what its about, quickly right what's on my mind before it disappears, and then save and close it after I'm done and just go on with my day. Enabling yourself to write whenever inspiration hits is my first piece of advice. Please do not ignore your job or type while driving as this will be detrimental in the long haul.
So here's my first piece of original advice, skim the internet for guides. Now before you start reading fanfics and whatnot what I mean is google websites and blogs about writing. Websites like Standoutbooks, Deadrobotssociety, and Writingexcuses are all wonderful free places to start! Here's where the word skim also becomes important; do not get bogged down by a single site. Spend your time shopping around, metaphorically of course. Wherever you go to learn about reading in this first step should cast your net as wide as you can and to be like the wind, never staying in one place for too long.
Still on the same subject of reading an researching is to do something book lovers enjoy doing, go to your schools library! I go to a community college and even the small college's library is enormous, with hole sections dedicated to things like psychology and ethics. As you may have guessed there is a whole section on how to write books! Free books about how to do the thing you want to do written by professionals doing the thing you want to do. It is a beautiful thing.
My recommendations for learning how to write can also be summed up with this, read books about how to structure your novels. The ideas come from within and reading about how to come up with writable ideas is useless until you learn how to properly structure your writing. Your notes made about stories in your head will remain that way if you don't understand the fundamental concepts of Plot, Characterization, Theme, Symbols, Syntax, Setting, Pacing, Character Arcs, and Genres. If this seems daunting, that is because it is! It is the majority of what writers must comprehend in order to consistently write compelling stories.
After you comprehend these basics then you will be where I currently stand, this is not to say that I have mastery over the fundamental concepts that I stated above, but that I have made as best use of them as I can, for now at least. Now that you have a working understanding of what the body of work should look like, it is time to dress the story and add your soul. To me the soul of the story is what you, specifically as a person, can bring to this story. If you give two writers a prompt or even set out a whole plot for them then they will write the story in two separate ways and the story will read differently. This is because they have their own soul to add. So soul then is also the way you go about telling a story; and mood, tone, and word choice seem to be the most prominent to me. Romeo and Juliet can be told in so many ways, it can be told like a horror story, two families rivalries bring two children to commit suicide, and a dastardly priest helps the two die. Or it can be told happily, two lovers having enjoyed each other for what seemed like forever, drifted off to be together for eternity.
Once you understand structure and have picked out what soul to imbue your story with you can go back to thinking of ideas to write about. You will increase your knowledge of all that you already know by writing more and more. The more you write the more you can learn from your mistakes and the more you can enjoy your successes. As the screen-wright Aaron Sorkin has said, "You can't be afraid to write crap." Everyone writes terribly throughout their career and you have to get over yourself and move on.