Host and Client share Canvas?

I created a fairly simple 2D card game app that I'm trying to turn into multiplayer. The game is played on one canvas. I copied a Lobby app, and I can get a host and client into the same scene, but they each get their own copy of the canvas, so they aren't really playing with each other. Right now, it's essentially a rummy game for a solo player against three robots. I will eventually make it into a turn-based game, but I need to get both players to see the same tabletop/canvas. Is this enough information for someone to say what I need to do?