Help with lineup settings on NFL.com

Can you change the lineups settings in a league on NFL.com once the league has been made. My friend is the LC and originally made the league with a RB/WR. When I joined the league and saw the settings, I mentioned to him about possibly changing it to RB/WR/TE since the TE position is becoming much more prominent in the current game. I mentioned that last year's runner-up was stuck with Witten on the bench because he also had Gronk and couldn't work out a trade. He agreed it was a good option to have for someone hope happens to make a good pick like that to cash in on. But, he told me he could not figure out how to switch the RB/WR to RB/WR/TE. Is it possible? If so, can some give me a run down so I can tell him. TIA