Never tried using the editor in an online game, but i would assume for him to use it anyway he would have to have paid for it separately on him steam account. You allowing in-game editor to be used online just means that you are allowing other users to use it if they have bought it.
You can just edit his team for him if he needs something done....
Hmm, when you started the online game did you click "allow players to use in-game editor" (something to that extent)? You need that ticked for everyone to be able to use it!
I don't see that option in online game preferences
You have to do it when you start the network game. When you are selecting what leagues and stuff you want in your game