The "Add Garment" light on the display panel is a special feature of the Whirlpool Duet washing machine. It lets you know when you can add items to an already started load of laundry. In some instances, the machine will leave the light on or even leave the door locked with the light on at the end of the cycle. You can troubleshoot the problem on the spot.
Wait for seven minutes after you start a wash cycle to see if the light goes off by itself. The washer gives you seven minutes after the cycle has started to add any forgotten laundry. Then the light should automatically go off.
Press the "Pause/Cancel" button on the display panel. This should clear the display panel and remove the light.
Turn the "Cycles" knob to "Drain/Spin" if the light is still on and the door is locked. This can occur when there's excess water in the washer at the end of a cycle. Once the additional drain and spin cycle is complete, the door should unlock and the light will stay off.