Go to the Settings page, then click on From Phones.
Click on the gear icon, then on Settings in the drop-down menu.
Click on From Phones on the left side.
Enter your area code in the search field and click on Search Available Phone Numbers.
A list of results of all available phone numbers with the entered area code will show up.
Select a phone number and click on Activate Phone Number.
The activated phone number will show up in the From Phones list.