How to get it?

Hi, there!
I have a season pass from bugingangas fallout 4 for Xbox one. It says I got fallout 3 for free, but how do I download it?
Awaiting your reply, thanks in advance!
I have a season pass from bugingangas fallout 4 for Xbox one. It says I got fallout 3 for free, but how do I download it?
Awaiting your reply, thanks in advance!