You have to extract the roster onto your pc from as usb using Horizon ( put it in my desktop).
Create 2 folders
Name one Original and the other Edited
Put the roster in Original
Now open Horizon and navigate to the original folder and open your save
You'll see an option on the right that says, CONTENTS
Click that
that will bring you to the offset, right click on that and extract it to the folder called Edited (leave Horizon open, makes it much easier).
You can then use NHL View to view your rosters.
When you're done editing. Save
In the offset of the save on Horizon (which you left the program open) right click and replace that offset with the one you created in edited.
Save
Save to device.
Load up in Xbox.
I'd do a practice run to make sure your saves work instead of pouring in countless hours and finding out later nothing saved.
Good luck
YOu then need