A method of using an online system includes transmitting user information to a server through an external terminal to log in to the server. The server specifies a home appliance for a remote service based on the user information received from the external terminal and determines whether remote service activation of the specified home appliance is set, upon determining that the remote service activation of the home appliance is set. The server transmits operation information of the home appliance to the external terminal. The external terminal transmits a command signal to the server such that the home appliance is operated based on the received operation information. The server receives the command signal, and the server transmits the command signal to the home appliance such that the home appliance is operated.