Once you have that, download the code (green button "Download as ZIP") and extract it into your WinPython folder. Go into it by typing "cd GamestonkTerminal" into the terminal and press enter. The terminal should indicate you're now in that folder.
Once there, run the following command: "pip -r install". This wil take some time to complete, during which you can follow the links in the "API Keys" section of the Readme and follow whatever steps they require for you to get an API key (probably have to register an account, create an "application" and create a key - it'll usually be a long random-looking string of characters).
Once you have the keys, edit the "config_terminal.py" using notepad or preferably Notepad++ and put the corresponding keys where "REPLACE_ME" is at the end of each line (keep the quotes!).
If you've done all that, go back to the command prompt from before and run "python ganestonk_terminal.py". The terminal should be running.