When you are on your xbox dashboard go all the way to the right under settings, then click account, then a window will pop up on the bottom there will be a button for license transfer. Then it will tell you what you have to do.

At the end it will bring you to a history of all the things you have downloaded. When on that list re-download the things you need.

Also realize you can only do this once every 6 months i believe so make sure you do everything they tell you.