Regular XBox1:
You must use Action Replay. After file is loaded to the AR mem card, place mem card in your XBox controller. At the dashboard go to memory and copy file from the mem card to the proper area for mvp2005. Then once in game, load the rosters. If you start the game before you copy over the roster file you can't access it from within the game.
Modded XBox:
Start the XBox by opening tray. You should get your dashboard. Go to files manager and simply copy and paste the roster file from your mem card to the mvp2005 area. (I'm not sure exactly where to do it from the ftp program).