Can the almighty subreddit please help a novice?

Hey guys, I have been searching for an answer to a question and have not gotten a simple answer that I can understand, and most question on this server are about "How do I play multiplayer(on a server)"

So...my question is this: My little brother and I want to play a CTM map together, we play on a server together(the server is owned by someone else), but neither of us have any idea how just the two of us can play, any help will be appreciated.

EDIT: clarification