plug something into something(and plug something in)
to connect something to something else, usually by connecting wires together with a plug and socket. Plug this end of the wire into the wall.Plug in the lamp and turn it on.
To insert a part of some object into an outlet, socket, or some other receptacle, especially to make a mechanical or electrical connection: Plug the iron into the electrical outlet. I plugged the speakers into the back of the receiver.