I'm not in your draft in particular BUT the way the draft I am in (we use ESPN) you can only change your lineup until the player has played. I realize that seems self explanatory, but I HAVE had friends not understand. So essentially, anyone on the Steelers or Patriots now cannot be moved from their locations (whether they were in the lineup or on bench). But all other teams right now you can change until 1 hour before their team's particular game.
Hopefully that made sense!
ps. @Katie I forgot to click "reply" to your specific question