Related Questions:
Add multiple numbers to a contact?
Add second number to a Contact
Add another phone number to an Account
Answer:
There isn't currently a field for an additional phone number in Event Temple for Contacts or Accounts, however it is possible to create a Custom Field to record this information.
We recommend using a Text custom field, which will allow you to add numbers, symbols & letters - eg. (604) 555 4891 extn. 55