HP Deskjet F4480 - Manual (Page 28)

Remove all paper from the main input tray.
b. Load envelopes.
Insert one or more envelopes into far-right side of the input tray, with envelope
flaps on left and facing up.
Slide stack of envelopes forward until it stops.
Slide paper-width guide to the right against stack of envelopes until it stops.
Load media 25
Paper basics