Samsung ML-2550 Series - Manual (Page 211)

P ROGRAMME I NSTALLING P RINTER O PTIONS F.4
3 Hold the memory DIMM so that the notch and the
connection point are aligned with the slot as shown, and
insert it all the way into the lower slot labelled “RAM DIMM”
at a 90 degrees angle.
4 Replace the control board cover and tighten the two screws.
5 Reconnect the power cord and printer cable, and turn the
printer on.