1. Find a smooth and empty surface such as the pages of a new notebook, or one of those empty rectangles on the Internet, or a wall of polished marble, or a volleyball, etc.
2. Find something suitable for making marks on that empty surface, such as a pen or pencil, or a computer keyboard, or a hammer and chisel, or a magic marker or whatever.
3. Scribble and scribble and scribble on that empty surface until you are very tired.
4. Play with cats to help you cope with the heavy workload and restore your energy.
5. The next day, and the day after that, and the day after that and so forth, repeat steps 1 through 4.
6. Repeat step 5 until you are rich and famous. (If you actually enjoy writing or otherwise feel somehow compelled to do it, you may continue writing even after this point.)
There are billions and billions of books which claim to tell you how to write, but what they actually attempt to tell you -- or what they claim to attempt to tell you in the cases where their authors don't actually care about you or your writing career and just want to sell books by exploiting your hopes and dreams, which might actually be almost all the cases -- is how to write well.
The thing is, people almost never agree about who writes well and who doesn't, which makes even those books written by people who actually care, worthless -- with one exception:
How to Write, by Gertrude Stein. This book is exceptional quite simply because, as everyone who has ever been anyone heartily agrees, Ms Stein wrote exceptionally well. Sistah came from Oakland back when there was no there there, and didn't play. Anyone who says she didn't write exceptionally well is probably either an innocent oaf or a very bad person who perhaps will try to sell you a worthless book or swampland in Florida. Watch out for the bad ones, and warn everyone you know, and strangers too!