IIS was just a suggestion since you are on Windows. I personally have never used it and not sure what it would take to get PHP working, I am sure you can google this. There are other users who have my app working under IIS, so it is possible.
The web root is defined in the IIS settings for HTTP server. You simply want to put the files in the folder defined in the settings. The files can be downloaded from Github using the zip link (https://github.com/salbahra/OpenSprinkler-Controller/archive/master.zip).
Also, if you are familiar with Apache you use that instead by downloading WinLAMP mini (http://prdownloads.sourceforge.net/winlamp/WinLAMP.4.0.0-mini.exe). This will install PHP and Apache on Windows. Again, either way works just giving you options.
Good luck.