Brother MFC-J450DW Basic User's Manual page 26

Chapter 2
f
Gently adjust the paper width guides (1)
to fit the paper.
Make sure the paper width guides touch
the sides of the paper.
g
Close the output paper tray cover.
h
Slowly and firmly push the paper tray
completely into the machine.
12
1
i
While holding the paper tray in place,
pull out the paper support (1) until it
locks into place, and then unfold the
paper support flap (2).
IMPORTANT
DO NOT use the paper support flap for
Legal size paper.
2
1