LMB on "Computer" -> Properties -> Advanced system settings -> Environment Variables... -> System Variables -> find "Path" string and click "Edit..."-> "New" -> paste python root path(D:\Users\Username\AppData\Local\Programs\Python\P ython36-32) and "Scripts" folder path(D:\Users\Username\AppData\Local\Programs\Python\P ython36-32\Scripts)
For windows 7/8/8.1, paste same paths through a semicolon without a spaces
python root path(D:\Users\Username\AppData\Local\Programs\Pyth on\Python36-32)
"Scripts" folder path(D:\Users\Username\AppData\Local\Programs\Pyth on\Python36-32\Scripts)