Canon BJ-200e - Manual (Page 25)

5. Arrange the stack of envelopes on a firm surface and press down
firmly on the edges to make the folds crisp. Press all the way
around the envelopes to remove any curls and expel air from
inside the envelopes. Also, press firmly on the area that
corresponds to the edges of the flap.
6. Align the stack of envelopes with the right edge of the sheet
feeder and slide in the stack until it stops.