Once you trade for a player you simply just need to go to your roster and update the depth chart. If they are a higher rated player they should already be towards the top, but double-check before going into your next game! If you make the changes in-game, that will only change it for that specific game.
a month ago
When you go to your franchise and select your roster where is he located on the WR depth chart? Make sure you put him at #1 or #2 from the depth chart at the menu, not while you're in a game.