What is the connection method for the wire plug? What are the main things to note?

Installation: Insert one end of the telephone's external lead plug into the landline's external lead socket, and then connect the other end of the telephone's external lead to the telecommunications office's external line socket. Handset installation: Before first use, install the handset with the rechargeable battery that comes with it, and then place the handset on the charging base. During charging, the "Charging" indicator light will light up and the handset display will show.