Open the SIM card tray: push the tray opener pin in the tray hole and slide the tray out.
If you have a single-SIM phone, put a nano-SIM card in slot 1 and a memory card in slot 2 on the tray with the contact areas face down. If you have a dual-SIM phone, put a nano-SIM card in slot 1 and either a second SIM or a memory card in slot 2 with the contact areas face down.