How to check codes and what they mean/

My son has a 96 mystique with the four cylinder. The check engine light came on last week and I would like to find out what it means. Can I use a wire on the connector under the dash to find out what it is? Also can someone point me to what the codes are and their meaning. I haven't had time to get a manual yet.

Thanks,
Bob

Take it to autozone. Theyll pull the codes for free with an OBD-II scanner and tell you whats wrong.