To make calls and use mobile Internet on your Nexus 5, you will need to insert an active micro SIM Card. If no card is inserted, the message “No SIM card” appears on the phone’s lock screen.
To insert the sim card you will need to eject the SIM card tray or slot. This is located in the right hand side of the phone. The eject button is a small hole just below the tray door(on the top below the Power on button).