I've researched this on different places, including stackoverflow, and I can't find an answer that helps me.
I'm using Windows 7, 64 bit, with Atom for 64 bit Windows. I have Python 3.6.1 installed in the directory C:\Users\Austin\Documents\Python. When I try to run a simple script to test Python in Atom, it says

'python' is not recognized as an internal or external command,
  operable program or batch file.
  [Finished in 0.083s]

I tried to run the same script in the command line, and it said the same thing. I'm new to programming, so please try to be a little patient.
None of the above answers worked for me. What did work, is installing Python from the Microsoft Store instead of downloading from the web and installing from an installer.
Why can't Python run in Atom?