Contacts can hold telephone numbers.
In the Edit contact screen click the Phones tab.
Click the Add phone button. The Phones table is loaded or has a new row generated if a phone record already exists.
Enter a new phone number in the Phone edit field.
Specify a Use type for this phone number. Use type definitions are reserved for administrators and users to establish.
Click the green update check icon. The new phone number is added to the table. The Add phone button reappears.
Click the Save changes button at the bottom of the page. The new phone number is written to the Registry.