psake-contrib is a repository for scripts, modules and functions that are useful for running a build with psake.
Step 1: Download the project zip file
Step 2: CD into the directory where you downloaded the zip
You will need to "unblock" the zip file before extracting - PowerShell by default does not run files downloaded from the internet. Just right-click the zip and click on "properties" and click on the "unblock" button.
Step 3: Extract the files in the zip
Step 4: Use the scripts and modules in your build
The following is an excellent technet article on how to "dot source" a script
Type "help about_modules" in PowerShell for help on how to import, load and use modules