I asked how do you get one as in create one like a folder
Open Wordpad or even just Notepad. Add code, go to "Save as...".
WORDPAD: Click on the drop down menu that says "Save as type:". Choose "Text Document". Save it with the name "Server.cs".
NOTEPAD: Save as "Server.cs"
Thats it, CS files are just Text documents. If you didnt know that, you're probably gonna have trouble actually making something.