Wiktionary
a. that gives advice or instruction on a particular topic alt. that gives advice or instruction on a particular topic n. practical advice on a particular subject.
Wikipedia
A how-to is an informal, often short, description of how to accomplish a specific task. A how-to is usually meant to help non-experts, may leave out details that are only important to experts, and may also be greatly simplified from an overall discussion of the topic.
One of the earliest how-to books was published in 1569 by Thomas Wight and entitled, A booke ohrijf the arte and maner, how to plant and graffe all sortes of trees: With divers other new practise, by one of the Abbey of Saint Vincent in Fraunce by Leonard Mascall.
Usage examples of "how-to".
It happened to people who read too many how-to books and became terminally strange.
In fact, written how-to instructions for stress inoculation were recently provided test-phobic students (Register, Beckham, May & Gustafson, 1991).
In 1971, I was persuaded to write a book entitled The Sensuous Dirty Old Man, in which I gently satirized sexual how-to books such as The Sensuous Woman.