How to get the terminal working?

Hello everybody,
I've tried to get instructions like:
bin/gpm install login
bin/grav newuser
To work from the command line, but nothing seams to work. I keep getting that bin is not recognized as a valid command.
I'm at the webroot folder for sure. Is it something I'm missing from the DOS side ?
Apologies I'm a newbie for all matters, but quick leaner...
Thanks for your help

Maybe this CLI guide will help you get started?

Also I would mention that to run these commands on windows you either have to:

1) Have PHP in your path (http://stackoverflow.com/questions/7307548/how-to-access-php-with-the-command-line-on-windows)

2) Prefix the bin/grav with PHP, i.e. c:\path o\php.exe bin\grav newuser

If your using GitBash or something you can use the more unix-like forward slash approach: /path/to/php.exe bin/grav newuser