Press the [User Tools/Counter] key.
Press [Tray Paper Settings].
Press [Tray Paper Size: Tray 1].
Select the envelope size you want to set.
Press [OK].
Press the [User Tools/Counter] key.
For details about the available paper size, see Recommended Paper Sizes and Types.
After specifying the paper size, select "Envelope" as the paper types using both the User Tools and printer driver, and specify the thickness of envelopes. For details, see "Printing on Envelopes", Print.