To qualify you need to not have used the app before and be silver membership. If you get "promotion not available" move on and try the next promotion.
1) Epix One Month of Xbox LIVE Gold Offer
2) IGN Members One Month of Xbox LIVE Gold Offer
3) iHeart Radio Get a Free Month of Gold
4) Free Month of Gold for Crackle Subscribers
5) Free Month of Gold for Amazon Prime Subscribers
6) VEVO users One Month of Xbox LIVE Gold Offer
7) Free Month of Gold for Syfy Subscribers
8) Free Month of Gold for Muzu Subscribers
9) Manga One Month of Xbox LIVE Gold Offer
After you sign up make sure to turn off Auto-renewal in your account settings.