They won't let me add one via the web page. It says I have to call. I assumed this was because I'm on a legacy plan and they want to tell me in person that I can't add it without moving to the new plan rather than just admit it on the web page. It may be super easy once you call but I never voluntarily call cell phone customer support because I'm not a masochist. Good luck.
In the end its just going to hasten my departure to Verizon. My daughter needs to be on Verizon due to her college choice so I might as well just move everyone.