In My Verizon under your phone number, you have the option to have two numbers listed.
Go to My Verizon>Account>Account Profile
Scroll to Billing and Payments> Change Home Phone
To add a number to the account beyond this, I would suggest contacting Verizon Customer Service. Go to http://www22.verizon.com/content/ContactUs/ for all means to contact Verizon--phone, email, online chat. For chat, the link becomes active after the page fully loads.