sign in to xbox 360 with xbox one account

If you sign into the xbox 360 account on your xbox one, and if the 360 Game/DLC is backwards compatible you can download it onto your xbox one and then if you want to use that game/dlc on your other xbox one account, you can just sign into both that 360
account and your xbox one account at the same time and launch the game on your xbox one account.

the xbox one account is also the xbox 360 account, they are the same

just sign into the xbox 360 with the same account as your xbox one.

your old xbox 360 account will most likely be attached to an older email account, nothing can be transferred.

It is possible to sign in on both the Xbox 360 and the Xbox One at the same time with no issues to your account.

"You'll be able to be signed on with the same gamertag on both an Xbox 360 and an Xbox One console at the same time," wrote chief Xbox One platform architect Marc Whitten. "However, like today, you can only be signed into one Xbox 360 and one Xbox One at
a time."

Hello WaterWolf3003,

Thank you for posting on the Xbox forums. We understand that you are attempting to sign in to your account on an Xbox 360, and the console gives you a message stating that the account is already in use. It is possible to be

signed in to one Xbox One console and one Xbox 360 console at the same time. However, there are some apps that you can't use on different consoles at the same time. Are you using an Xbox 360 backwards compatible game on the Xbox One when you are signing
in to the Xbox 360? The account cannot be used on the Xbox 360 when you are using an Xbox 360 backwards compatible game on the Xbox One. Be sure to let us know the results!

If your Microsoft account has an Xbox Live Gold membership, it is usable on both Xbox One and Xbox 360. Just sign into Xbox 360 using that same account that you use on Xbox One.