Complete instructions for using the Pittsburgh Plan can be found in Galileo Rising, by Richard T. McCoy, Ph.D.
This short book by the Plan's founder lays out the philosophy of the Plan and then provides detailed instructions on every aspect of the Plan, ranging from the very general (where, when and how to conduct a session with your child) to the very specific (detailed step-by-step instructions relating to the content of a particular worksheet).
You can get started by using the QuickStart Module (containing detailed, step-by-step instructions for the first 10 worksheets) or by downloading Chapter 10 of Galileo Rising (instructions for the first 33 worksheets)