Ok, first you need XTAF, Winrar, and a usb drive.
Im going to assume that you have all that. but if not, pm me for help

Download the beta
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and this modded profile
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I recommend doing this but if you know a quicker way, feel free to use it.
go into winrar and extract both files to your desktop

then go into xtaf with usb drive plugged in
after that go into the content folder. right click, and inject folder. find the folder for the profile and place it into the content folder, it should be E000000000***** something not exactly sure

then in the content folder there should be a bunch of zeros, click that so it opens and then inject folder and insert the beta, it should be 4D5389B9

then place in xbox and there you go
+rep if helped

files obtained from xbox360iso