Can you talk? Because if you can, you can write. Probably not like a pro, but you can write well enough to get your point across. But so many otherwise very bright and articulate people go into a catatonic stupor when faced with a blank white page, or computer screen.
One of the best ways to bring yourself out of that is to talk. To a friend. To a colleague. To your teddy bear. Anything. Just say what you want to write about. It’s a good idea to have a tape recorder there because you’ll be surprised at some of the turns of phrases you come up with and you won’t remember them, even though you’re sure you will. Then, play the tape back and listen to it, and see how it sounds to you. If you like it, write it down.
Do not try to improve it. You can get yourself into trouble with that. That doesn’t mean you can’t change anything, but don’t keep rewording one phrase until you get it just right. Trust me, you’ll be there all night.