Your extensions should match your main greeting. If you have not setup a main greeting learn HERE

Step 1: Add a Employee Extension

Navigate to the Extensions on the left hand menu. 



You'll see "Employee Extensions" under department extensions. Select the "Add Extension" button.


A new extension will appear at the bottom of the list. 

Step 2: Customize Your Employee Extension

Select the edit drop down menu.  

On the left column of the extension menu you can select the extension number and enter an extension name (Ex: John).

On the right column you can add call forwarding numbers, set email addresses for voicemails to forward to, and add a voicemail greeting for the extension.