To setup a Directory Number go to Configuration > TRACK Pulse tab > Directory Number. Click on the +Directory Number button in the top right corner to create a new Directory Number.
Once on the Create Directory Number screen, fill out the following fields:
Name: Name your Directory Number. The name you enter will be able to be selected throughout the system whether within setup functions or within the agent dashboard when you need to transfer a call.
Number: Enter the phone number of directory number.
Can Agents Use?: If this option is selected then an agent can transfer a call within the agent dashboard to the directory number.
See What is a Directory Number?