Instructions
Insert your USB flash device into the computer. Before you can transfer the codec to your console, you must put it onto onto the USB flash device.
Click "Show Files."
Open the folder that contains your downloaded codec. Click the codec and slide it into the window with your USB flash device files.
Remove the USB flash device from your computer and insert it into a USB slot on your Xbox 360.
Power on the Xbox 360. Software designed for the Xbox 360 is designed to automatically boot with the Xbox 360, so no further action is necessary.