This is really simple ,
Just insert Disc 3 to your Xbox , go to xbox live and pick the 1st Legend map . You can play with 2 controllers if you set it up to easy and complete one stage , or just find someone random online and complete it together .
Also if you have a friend that is playing the game is even better because you can complete all the Legend maps .
Below you will see a video guide so you get the idea with Legends of the wasteland .
Good luck :)