Newbie MySQL Q: setup for collecting registrations in database

I took over a project which has a contest registration page with captcha, and a comments page. Both forms have the post method all set up, but I need the information to go into a database for my client to pull into Excel.

I have a book on MySQL and it shows me how to create tables but I’m not understanding if I’m to use the existing database for the WP site and create a new table, or do I add another database to the site and create tables just for the purpose of collecting names, etc.? And do I need to have a routine set up to tell where the “post”ing item in the forms should go? In the existing database or a new database?

HELP! I figured I could find a simple plugin for this here, for collecting data into a database, but it’s not showing up in my searches.

My goal was to use WordPress to make the site content manageable by my client. That part has succeeded, but this collecting the form data for the database is a new thing to me and I have to make this work, and soon!

Do I download the existing database and create a new table using Terminal on Mac OS X, or do I create it online through the server?