Update install instructions for Windows

docs/source/Setup/Installation-Troubleshooting.md

@@ -83,6 +83,7 @@ If `localhost` doesn't work when trying to connect to your local game, try `127.
 
 ## Windows Troubleshooting
 
+- If you install with `pip install evennia` and find that the `evennia` command is not available, run `py -m evennia` once. This should add the evennia binary to your environment. If this fails, make sure you are using a [virtualenv](Installation-Git#virtualenv). Worst case, you can keep using `py -m evennia` in the places where the `evennia` command is used.
 - Install Python [from the Python homepage](https://www.python.org/downloads/windows/). You will  need to be a Windows Administrator to install packages. 
 - When installing Python, make sure to check-mark *all* install options, especially the one about making Python  available on the path (you may have to scroll to see it). This allows you to
   just write `python` in any console without first finding where the `python`   program actually sits on your hard drive.

docs/source/Setup/Installation.md

@@ -31,6 +31,8 @@ Once installed, make sure the `evennia` command works. Use `evennia -h` for usag
 
 ## Initialize a new game
 
+> Windows users: You need to first run `python -m evennia` once. This should permanently add the evennia launcher to your environment, making the `evennia` command available.
+
 Use `cd` to enter a folder where you want to do your game development. Here (and in
 the rest of the Evennia documentation) we call this folder `mygame`, but you should of course
 name your game whatever you like.