Firstly you will need to login into your members My Portal page. Once there navigate to the VoIP tab. Then click on the Cloud PBX tab. You'll find Login to Phone Console button, click that, which will redirect you to the phone console dashboard.
From the left click on Configuration to expand the menu. Click on Custom Destinations.
Click the New Custom Destination button, to create a new Just Dial destination.
Then drop down the Type menu and select the Just dial option.
Then fill in the Name and Dial field, see the example. Leave all the others as default and then click the Save button.
Now you have created a custom destination that you can use in anywhere else in the phone system.