Add background to 3d game,How do I add a background to my 3D game?

I have a simple 3D game, where my character can only move in x and y directions. Is there any way to add a background to this game? I’ve tried making a new canvas with the image, but it displayed the image over my game. Any help is appreciated!

You can put a plane behind with a material, or you can add a skybox, if you want to change the background sky