Open the script (myscript.ps1) in Windows Powershell ISE
Press F9 at the variable you want to inspect (debug). For instance 2nd line in the sample below where the $outputText variable is being assigned
In the shell window provide the relative path of the script along with the param value. For instance: .\myscript.ps1 "my value"
Hit enter (you don't need to hit F5)
You'll be able to see the debugging breakpoints in highlighted with yellow color. Place your cursor to the desired variable to inspect the current value.