User guide

A user guide, also called a user manual or (less frequently) instruction manual, is a book about how to use something.
A computer usually has a user guide to tell people how to use it. A computer program also often has a user guide. 
The user guide is often written by the person who made the software. 
People who want to write a user guide must keep the words very simple so other people can understand what you are saying. It also helps to put many pictures into the user guide. 
If there are pictures, people who read or speak a different language can still understand what to do with the equipment or software.