If your league allows players to be placed on injured reserve, this is the screen to place players on IR or to activate them from IR. For active players, in the "Action" column, select "Place on IR" for the players you want to switch from active to IR. For players already on IR, select "Activate". If the commissioner has indicated in the league rules that activating or placing players on IR require commissioner approval, then any transactions from this screen will be submitted to the commissioner and not executed unless the commissioner approves it.
When the commissioner sets up the league, he will enter a weekly "Lineup Deadline". It will not be possible to enter transactions after that deadline. Also note that it is not possible to enter transactions from Sunday 1:00pm EST to Tuesday, 7:00am EST.