Simple 2-player sports game?

I'm trying to figure out how to have two players connect to a game with a single controllable character on each side, like a one-on-one sports game. I know nothing about how to get the networking elements to work, and most of the tutorials I've found just explain it as multiple 3D controllers that are prefabbed and instanced. This would be 2D, and have two characters already out on the field that are being controlled. Based on how I'm controlling things, I would just need to relay the position and 2D velocity of the player, along with button presses. Obviously I'm not expecting it to be perfectly in sync, but I just don't know where to begin with it.

 

Can anyone help or give any suggestions? I'm brand new at multiplayer, so I don't understand how to use the networking tools at all, and they all seem to be geared towards creating instanced players, not controlling ones that are set for the level.