From a conversation press transfer. Listen for dial tone (during this time the original party is on hold). Dial the phone number of the second party. When that party answers, announce the conference. Press transfer button and the three parties are joined.
Instructions for a busy/ no answer:
From a conversation press the transfer button. Listen for dial tone. Dial the phone number of the second party. If the line is busy or there is no answer press the cancel button to return to original conversation.