Playing in multiplayer mode in Marvel Battlegrounds is easy – simply load any of your Marvel figures onto your Disney Infinity Base and play. The base will log each character into the in-game selection screen library, where they will remain for the entire Versus play session. Once you've loaded the character into the game, the figure is no longer required to stay on the Base for that play session. However, they will need to be reloaded after closing the game.
Multiplayer in Story and Challenge modes is just like any other play set multiplayer functionality. You put each designated player onto their slot on the Infinity Base.