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.