Canon 3743B002 Basic Manual page 47

Open the Paper Support.
(1)
Do not raise the Paper Support.
Open the Paper Output Tray gently, and open the Output Tray Extension.
(2)
Slide the Paper Guides (A) to open them, and load the envelopes in the center of
(3)
the Rear Tray WITH THE ADDRESS SIDE FACING YOU.
The folded flap of the envelope will be faced down on the left side.
Up to 10 envelopes can be loaded at once.
Slide the Paper Guides (A) to align them with both sides of the envelopes.
(4)
Do not slide the Paper Guides too hard. The envelopes may not be fed properly.
(B) Rear side
(C) Address side
3.
Specify the settings in the printer driver.
Select Envelope in Commonly Used Settings on the Quick Setup sheet.
(1)
Select DL Env. or Comm. Env. #10 in the Envelope Size Setting window.
(2)
Select Landscape in Orientation.
(3)
Select Envelope in Media Type.
(1)
Select DL Envelope or #10 Envelope in Paper Size.
(2)
Select the landscape orientation in Orientation.
(3)