Link the Xbox live account you use when signing into destiny Or if you are talking about to change account linked on app to different one, go to home screen of app, hit the menu button on top left, on the bottom of list should be setting button click that, go to account settings, and on bottom of that screen it should sat sign out, then you can enter whatever other Xbox live account you want. (Note I'm on android device, idk if it's different on iphone)