Important: Use a standard micro SIM only. Inserting a smaller size SIM (such as nano SIM with an adapter or a modified SIM) may cause the card to not fit properly or damage the card slot.
Take the back cover off.
With the SIM card’s gold contacts facing down and its cut-off corner facing in, insert the SIM card all the way into the SIM card slot.
Push the SIM card in until it clicks into place.