I don't get what's confusing to imagine how it would work?:p
Go into a lobby, select 1 vs 1, perhaps both players get the option to choose how big their playspace is , cause some people might not reach the other if they have less roomscale then the other, or some "get close to each other technique" which might be implemented in later on.
All that's left is just each person controlling one character until the other dies ^=