While engaged in a conversation, press the "Scroll" key once and the corresponding soft key under CONF.
Make another call, either intercom or outside, press the CONF key and receive conference tone.
Make another call or press the CONF key to join all parties.
Repeat the last step until all parties are added.
To drop a party from your conference call:
Press CONF and dial the extension or line number that is to be dropped.
Press CONF again to reestablish the conference.