1) Lift handset or press speakerphone

2) Dial the extension of the phone you want to speak with

3) When the person answers the phone start speaking

 

If the other person in on the phone depending on the phone settings the call may go to voice mail.

 

There are settings in the phone itself that will make this option work differently that described above but the above instructions will be accurate if NoContractVoIP.com programmed your phones.