With screen facing down, open the SIM/SD card cover.
With screen facing down, pull out the SIM card tray.
Place the SIM card into the tray with the card's gold contacts facing up and its cut-off corner facing out.
Ensure the card is properly seated in the tray with the front of the card under the notch and gold contacts facing up.
Press in on the tray to lock it into place.
Close the slot cover and carefully press the cover until it clicks into place.