You'll have to visit ChaCha - Mobile Search | Text Search | Questions and Answers. At the bottom of the page, you'll see a link for "Careers". When you click on that, you will see "Become a Guide" in the top right portion of the page. They are not currently hiring new guides, but check back frequently, as they very frequently hire. I think "KGB" is a competitor, so you may try them, as well.
In case you're wondering, you merely fill out an on-line application and complete the on-line training program (only takes an hour or two) on how to correctly answer questions, etc. After passing your "final exam", you are good to go.