From the conversation press transfer. Listen for dial tone (during this time the person you were talking to is on hold). Dial the desired extension. The phone will ring in that person's office. Announce the 3-way conference. Press transfer again and now the three parties are joined.
From the conversation press the conference button. Listen for dial tone. Dial the phone number that you want to call. If the line is busy or there is no answer hit the cancel button to return to original conversation.
