To make Corsix-TH run properly, you first need to have an original copy of Theme Hospital or a demo version (available for download on Uptodown). Once you have it downloaded, you just indicate the filepath where the game is saved and Corsix-TH will take care of the rest.
The rest includes letting you to play Theme Hospital with lots of improvements made to the original version, support for screen resolutions found on modern machines (up to 1920x1080), and even some additional bug fixes. That said, if as usual you use the demo instead of paying for the full game, you won't be able to enjoy all the features.
Corsix-TH is an essential tool to enjoy the brilliant Theme Hospital. Not only does it let you run it on any operating system, it also substantially improves the experience.