http://www.gameinformer.com/b/news/archive/2015/03/02/xbox-one-games-with-gold-titles-can-now-be-39-purchased-39-through-xbox-360.aspx
Players can now reserve their free copies of Xbox One titles offered through the Games with Gold program through the Xbox 360 dashboard. The move is meant to make it easier for Xbox 360 owners who don't yet own an Xbox One to reserve their virtual copies of the games offered up each month.
Starting today, the Games with Gold section of the Xbox 360 dashboard also contains the Xbox One titles provided by the program. Once there, the menu features a "Free on Xbox One" section, which allows players to "purchase" the games on promotion for free. Players who already own the selected title will see "Play on Xbox One."
Previously, Xbox 360 owners were required to sign on to the Xbox Live website in order to purchase Xbox One games. The Games with Gold program offers monthly free game downloads to subscribers of Xbox Live Gold. Players own the rights to games redeemed through the program even if their Xbox Live Gold subscription lapses. Games with Gold's March titles recently went live, making this the perfect time to try out the new feature.