Ok i guess you want to host (create) a server ,instead of creating a new map. (1)
Creating a server is a bit tricky, if you don't know that much about servers in general.
But you can use our search function, we got tons of topics about it. (e.g.: [[MISC]How to set up your own working online server on Windows.
Before asking new questions about hosting a server, please try to get it working on your own (+reading topics).
But feel free to ask, if you run into problems
However, i think it would be more easy for you to join existing servers with your friends, you can search them via Server Browser easily.
(1) Hosting a server means that you run an already existing map in your own environment to play on it. You can download maps from other servers (or take official ones).
Creating a new map means ... you create a new map using the editor.
Edit: He was faster