Would you try to make a cabinet without knowing some basic carpentry skills? No, that would be idiotic, right? You'd be an idiot if you tried to fix your car without knowing a little about auto repair.
Writing is exactly the same. It's a craft. You're going to end up with a big mess if you don't have the basic skills, and acquiring those skills takes time. Sadly, writing isn't really taught anymore, not in high school, not in college, not in most writing workshops, not anywhere. Maybe it's supposed to be sacred and holy. I don't know.
I'm very lucky – my father is basically a 10th degree black belt in writing. He taught me the craft of writing from a very early age. I got my black belt from him, and I'm passing on some of his wisdom right here. Anyone can learn to write passably well if they put in the time.
An editor will stop at the opening paragraph of your manuscript if you don't know the basics of grammar. For instance, the difference between "it's" and "its": this drives people nuts, myself included. It screams "amateur" in a booming evil robot voice.
The best way to learn a skill is to teach it, so I highly recommend teaching English grammar to adults, non-native speakers who really want to learn the language. Why adults? They're motivated and attentive. Kids will just goof off and waste your time.
If you live in a big city, I guarantee there are teeming hordes of people dying to learn English. Lots of churches have free English classes, they'd be happy to have you. Hell, tack a flyer up in the Egyptian café down the block, you'll have five emails within a week.
Any old grammar textbook will do. It's not going to be thrilling, but if you're not willing to put in the time, you'll never get past tormenting your family and friends with your ungainly prose.
A sentence can obey all the laws of grammar and still be a steaming turd. This is where style comes in. Style is more elusive than grammar; it's where you can begin to express yourself. Consider the very text you're reading right now; the style is different from how I'd write a book. It's "colloquial", because
I'm giving a sermon I'm trying to create the impression we're having a conversation.
There are some iron laws of style that you violate at your own risk. For example, the dreaded "passive voice". It should be used as infrequently as possible. If you know what the passive voice is, you're already typing up a snarky comment. If you don't, you need to learn. And chances are you need to learn a lot of other things, too.
There are a few classic books on style out there, (H.W.) Fowler's English Usage, and William Strunk's The Elements of Style. Check them out of your library. Read them. Live and die by them.
Finally, after all your hard work, you're ready to do what you actually wanted to in the first place: tell a story.
Storytelling applies to nonfiction just as much as it does fiction. It's the most seminal human art form, more primal than cave paintings or dancing around the fire to animal skin drums. I don't have a time machine to prove this, of course, but it's what I believe. Learning the basics of storytelling, the "principals", as Robert McKee would say, is critical, even if you're going to violate them.
Speaking of Robert McKee, I love his book, Story. Even if you come to the conclusion he's a hack, you'll be better off; you'll know what to hate.
There's really no substitute for reading. So read a book. Twice. Watch a movie. Twice. Break things down, think about the grammar (movies have grammar, too!) and the style and the storytelling. You'll learn more from watching Die Hard twice than you will from any workshop or "prestigious" graduate school writing program. I promise you.