From the top edge of the device (display facing up), remove the card tray.
Utilize the insertion/removal tool (or a paperclip) to unlock the tray by inserting it into the provided slot (figure 1) then remove the tray (figure 2).
Insert the card as shown (gold contacts facing down).
Insert the card tray (gold contacts facing down).
Press in on the tray to lock it into place.
Check out these interactive demos (S10e, S10 or S10+) for more info.