Steps

1)Get Horizon: [ Register or Signin to view external links. ]

2)Open Horizon

3)Make Sure You Have A USB Flash Drive And Go To Your Xbox and Copy A Picture Pack From Your Xbox To The USB.

4)When You Have Done Step 4^ Explore Your Device In Horizon And Open The Picture Pack From Your USB Into Horizon And Make Sure It Shows Your Gamer Picture IDs

5)Download The MW3 Prestige Picture Pack Here: [ Register or Signin to view external links. ]

6)After You Downloaded The File Put It In Horizon.

7)After Step 6^ Copy All The IDs ,From The Picture Pack You Got From Your USB, To The MW3 Prestige Picture Pack.

8)Now Reash and Resign The MW3 Picture Pack

9)After Step 8^ Put The MW3 Picture Pack On Your USB

10)Now All You Have To Do Is Just Plug Your USB Back Into Your Xbox

11)Put The File From The Mw3 Picture Pack To Your Xbox

12)Just Edit Your Profile Gamerpic And Find The Mw3 Pics And Boom There You Go!

13)Enjoy

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I Hope This Helped!