This download is a ZIP archive. Decompress it, take a look at the README file, and get started working through Getting Started with Macaw!
P.S. You'll build your own copy of the Macawfrence project in the course of working through the book, but if you'd like a copy, here is Macawfrence.mcw for your reference.
Copyright © 2015 Joe Chellman and Rex Rainey