problem in xbox user (games app)

hey all..
im new here!!
great forum by the way!

now for my prob:

when i install win 8 i didnt fill the correct user of my xbox 360 and now i dont know how i change to the right user.
i talk about the games app that come with the windows.

(i didnt find the smartglass app that everyone talk about)

someone know what to do?

tnx!!