If you have to call another individual and bridge them on the conference with the existing caller, then you must go to your phone book and press the call button. Once the call is connected with the individual, then the original call is automatically put on hold and you have a sign stating "MERGE" or "CONFERENCE" on your handset. Upon pressing this button, the call between 3 parties i.e you, the original caller and the individual whom you bridged now is active.
Hope this answers your question.
