Start the game. Copy the long text code in the github, then open console (for Firefox just right click anywhere on the game page and choose inspect, then select console) and paste the code and press enter (you can close the inspect/console window). Tool will show itself. Write mm, wilson, $, sub, love, etc in the box and it will list connected variables/values, then you can add them on your list, change their values or freeze the values or just watch them.
Nothing complicated, very simple to use tool.