multiplayer on switch

forgive the idiot question, i have a nintendo switch, got it mainly to play mario cart with kids, but cant figure out how to do two player, do i need to get another controller, or can it be done with the two side controllers that came with it, it will be plugged into the tv.

Is it a Switch or a Switch Lite?

The Switch has detachable joycons the Lite doesn’t.

I may be wrong but I dont think you can do 2 player on the Lite unless you have a second Lite and another copy of the game.

Edit*
Just reread your OP, you should have the option in the game to choose multiplayer, it’ll then show you what to do with the controllers - ie detach them and hold them sideways