You want to give your players a status of Sub/Spare or Regular player.
Go to Teams (Menu, Manage, Players/Teams, Teams).
1. Select a division.
2. Click on a team,
Find the Roster List on the right hand side.
3. Select a player,
4. Pencil to edit.
5. Give your player a Status.
6. Save.
Hint: You can multiple select the players, to give them the same status.
You can add Player Status to your stats page. Subs/Spares will have an S.