In case no conference bridge was assigned to your account, you will not be able to access this feature:

If your system administrator has assigned you a conference bridge, you will be able to manage bridge options, as well as manage active conference callers with actions such as mute/unmute, pause and disconnect.

To start a voice conference simply go to the Menu and choose the CONFERENCE BRIDGE link.
A user can have one or several conference rooms assigned; in case more than one conference rooms are assigned to your account, choose the right one from the drop-down list placed on the upper side of the CONFERENCE BRIDGE screen (the ‘Use this conference room:’ option).
Once you have selected the right conference room, start adding participants by dragging & dropping them from the CONTACTS list. As soon as the first participant is added to the list, the call button changes from grey to green and you are ready to start the conference.
Users can join your conference just by dialing the conference extension (internal line) or the Direct Inward Dialing number (external line).

Browser not supported