The Environment Variable "Path" is used by the computer to find a program if the file path is not given. This is used by other programs as well and some will automatically update this variable when the software is installed. By the way, this is the same procedure for setting the tabcmd path (typically the path is C:\Program Files\Tableau\Tableau Server\yourVersion\extras\Command Line Utility just make sure to change yourVersion accordingly).
If there isn't a reference to PowerShell in your computer's Path variable then this walks you through the steps to add it yourself. It's very easy and requires no programming
From the Start menu, right-click on Computer and select Properties
Click Advanced system settings
Click the Environment Variables... button
Select Path and then click the Edit... button
At the end of the Variable value: append the following
Click the OK buttons then restart your computer.
Your Humble Tableau Server Padawan,