Keep in mind, you don’t have to set up a “virtual” server to playtest your game. The deal is, however, you’d have to get through a window where CS asks you to “upload” your game every time you restart the game.
All these terms don’t mean that you need online connection to playtest your game, for context.
Speaking of which, do you have an archive-manager program? The likes of Winzip, WinRAR, or 7zip. If you don’t, you have to get them to extract the CS .zip file.