To create a conference call, dial the first party that you wish to speak to. Once you are on the phone with them, press the soft key labeled CONF. The first call will be placed on hold and the caller will hear silence or music on hold if configured. When you hear the dial tone, dial the second party. You can wait until they answer and announce yourself if you wish. Once you are ready, press the CONF button again and your three parties will be connected.
You may repeat this behavior as many times as you would like, up to the limit of the number of call presences that your phone allows. Typically, this is two calls per line button. Note that you cannot disconnect a particular caller – they must hang up to leave the call.