my post man is nice.. so he rings the bell and hands it to me some will just throw in your house or the letter box if it fits
pos express, u have to use their ready made envelopes/boxes
just go to the post office, go to the counter to send parcels & ask for the envelope/box size that u want.
then fill in the details on the front n back, take the yellow tracking number at the bottom right & seal it
drop it into the post express post box (with a yellow label or its yellow in colour)

Pos Express envelope sizes (taken from the post above):
220 mm x 110 mm  RM 2.50 (Window/Non-window)
229 mm x 160 mm  RM 3.00
353 mm x 221 mm  RM 4.00
250 mm x 210 mm x 25 mm  RM 6.00 (Packet)
340 mm x 250 mm x 25 mm  RM 7.00(Packet)