In order to use SetACL efficiently, you need to know about the basics. Please read this article about Windows permissions as a starter.
SetACL comes in two flavors: a command-line version and a COM object. The former is a universally versatile tool that can be used manually, from batch files, scripts, installers and even full-fledged programs. The latter is accessible from COM-enabled scripting and programming languages only.
Documentation for the command-line version (SetACL.exe).
Documentation for the COM version (SetACL.ocx).
Benny Roos kindly converted the HTML documentation to easily printable PDF format. (Note: this document is current as of 2016-08-18).