Start a party chat using either the Xbox One party chat or the in-game Xbox 360 party chat.
Xbox 360 or Original Xbox to Xbox One party
To party chat with friends who are also playing on Xbox One, press the Xbox button , then select Multiplayer > Start a party. This works for anyone on Xbox One, whether they’re playing games made for Xbox One, Xbox 360, or Original Xbox.
Xbox 360 to Xbox 360 party chat
To start a party with friends using Xbox 360, go to the Xbox 360 guide while you're in the Xbox 360 game by pressing the View and Menu buttons at the same time. Then select Party > Invite Players to Party > Select the friends you want to play with.
Once your friend accepts your invite, you'll both join the party.
Free Xbox One Game Codes List
Playing a multiplayer backward-compatible game on Xbox One
Download Game While Playing Xbox One Games
If a game supports multiple players on the same console, you'll be able to add a second player to a game as you’d normally do on your older Xbox. Make sure both people first sign in on Xbox One.
Free Full Games Xbox One
Download Game When Xbox One Is Off
If you hit problems with backward-compatible party or multiplayer games, try the Xbox One Multiplayer Game Solution.