For details about how to change the paper size in the wide LCT, see Loading Paper into the Wide Large Capacity Tray.
After sliding the paper tray in, make sure that the paper size is changed correctly on the [Top] screen. To display the [Top] screen, display the [Home] screen and press the icon at the upper right corner of the screen.
You can load envelopes into the wide LCT. When loading envelopes, place them in the correct orientation. For details, see Envelopes.