1) Learn a programming language, everything about it and then some more.
2) Learn everything about Windows and how Windows works, which is significantly more complicated than "go into Control Panel and click this".
3) Learn many other programming languages since they are not all suitable for all jobs, some are better than others.
4) Write code, test, debug, test more, debug again, test some more and then test again. Do all the other add-ons for your game. Debug and test all of this.
5) Total time to do all of this: A few thousand hours and then some more most likely.