If you haven't already extracted a save or don't know how to do it then follow this Tutorial HERE
After you extracted a save from your USB Memory Unit you will now expand “Tools” and select the Package Manager. Once the Package Manager is open, Click "Open" in the top left corner. Now browse to the save file you extracted and select and Open it.
Now once the file is opened you will see your Profile ID, Console ID, and Device ID. Now click "File" in the top left hand corner again and select “Save ID's” and you can choose which set you would like to save your ID’s too so that you don’t have to copy and paste them every time you want to use a downloaded game save.
Now you can open any downloaded gamesave in the package manager, use the ID Set drop down box and select which set you saved your ID's to earlier. It will put your Profile ID, Device ID, and Console ID into the appropriate boxes. Now simply click the Rehash/Resign button and you can then inject the save back into your USB Memory Unit and you can now use the downloaded game save.
Edited by Caboose, 24 October 2012 - 04:40 PM.
Updated 360Rev Pictures