Login to your NextPBX dashboard. In the left-hand menu, click on the number you want to setup. Click on Configuration, then click on "Change Application."
You'll see five icons representing the five main applications we have. Click on the PBX icon in the main window.
A dialog box will appear warning that you are switching from a single phone number to a PBX with multiple extensions. Doing so will rebuild your number as a PBX, and your current messages and configurations will be deleted. If you want to continue, click the Yes button.
Your dashboard will then refresh, and on the left-hand side of your dashboard you will now have several new links: Add extension, PBX Setup, and six extensions to start with. You can configure each of these extensions just like a regular NextPBX number.
NOTE: You MUST stay in PBX mode in order to use the extensions. If you try to switch to another application (Voicemail, Virtual Personal Assistant, etc.), you will lose all of your extensions and configurations. You can still configure those applications for each extension when you are in PBX mode.