Go into "Roster Manager", and "Trade
Players". For example, if you want the New Jersey Devils to win
frequently, select their team, press Triangle, then cycle through the
teams. Look for very good players (90+ overall) and select a couple of
them. Trade them for players on the Devils such as Gionta or Stevenson,
who are not very good. Even if you trade a 70 overall person for a 90+
person, the CPU will accept. When you are done, go back to the "Roster
Manager" screen, select "Player Status", select the Devils, and scroll
down the player names. Dress the players so they can play. Then, return
to the roster manager screen once again. Go into "Edit Lines", change
the lines, and put your players from the other teams into lines.