Hi bej,
If you're looking to work with a MySQL database once it has been created, you can use phpMyAdmin. phpMyAdmin is a point and click method to manage a database (a MySQL GUI, much easier to use than running raw SQL statements). We have a general guide here for managing a database using phpMyAdmin.
I don't believe I understand your question 100% however. When you referrer to populating the database, are you referring to putting in sample data, or are you actually trying to setup the shopping cart?
If you can post a comment at the bottom of this page with a few more details on what exactly it is you're doing, I'm more than happy to look into this further and try to point you in the right direction.
Thanks!
- Brad