Windows PowerShell gives you the option to implement extra modules which can be used from within your scripts after invoking them with the appropriate command. For demonstrative purposes I will use the WASP module (Windows Automation Snapin for PowerShell) here. You can download it from:
After downloading, unpack the file and drag the contained WASP folder over to the PowerShell modules directory (C:\Windows\System32\WindowsPowerShell\v1.0\Modules). To use it in your script, place the invocation before any of the module's commands. The invocation is
Replace WASP with the name of the module you want to use. In the following script you can now use the commands associated with the module, e.g. select-window for the module I used.