How to use Builder?

Hello. I’m a Ruby newbie, so please bear with me. I have an object
named Contact that has attributes first_name, last_name, address1, etc.
I want to create an XML file in the following format:

<?xml version="1.0" encoding="ISO-8859-1"?> David Smith 123 Main St John Doe 321 First Ave.

How do I use Builder to create this XML output? Do I need to iterate
through the Contact attributes and convert into a hash before running

Thanks in advance