How did Asimov learn to write?

From Yours, Isaac Asimov

pg 9

"I honestly don't know how to write or how to advise anyone else to write. I can do it, but that doesn't say I know how to do it. I also synthesize DNA in every cell of my body, but I don't know the exact details of how I do that, either."

Asimov actually learned how to write first by reading voraciously as a young child, and having a desire to tell stories himself.

When he first started trying to break into John W. Campbell's magazine, Campbell would give him detailed advice, and in his autobiography Asimov says that he learned a lot from that.