HP Color LaserJet 8550 Multifunction Printer series - Manual (Page 211)

210 A DIMM Installation EN
8 Insert the formatter board into the
printer, ensuring that the edges of the
board line up with the guides in the
printer.
9 Tighten the thumb screws, reconnect
the power, and turn on the printer.
10 Confirm installation: print a
configuration page and compare it
with the previous configuration page.