Insert a SIM card eject tool or a paperclip into the small hole besides the SIM card tray, located on the upper section of the left edge of the phone.

Press to eject the tray.

This may require a significant amount of force.

When reinserting the SIM card, ensure that its contacts are facing to the rear side. The tapered corner of the SIM card has to point to the outer bottom corner of the tray.