Suppose I want to draw a horse. I don't know how to draw a horse so I buy a How to Draw Animals book and follow the instructions of the book to draw a horse. Now can I use my drawing for commercial purposes?
The book teaches you how to draw horses. Once you learned how to do it, and you draw a really nice horse, you have drawn it yourself. You have the copyright. You use it any way you like.
Of course it's different if instead of drawing the horse yourself you just make a copy of an image in the book. That would be the author's copyrighted drawing.