The CEL (check engine light) means that some problem has been detected and a code describing the problem has been stored in the car's control unit. You need a device to read this code so that you can start troubleshooting the issue.
For the home mechanic there is a device called the Durametric tool that can do this, and it costs about $300. Used ones can be picked up for $100 to $200. Now, fair warning - even if you get the tool to read the code, the message can be somewhat cryptic and will likely not point you directly to the problem unless you are experienced and know what you are doing.
Your best bet is likely to run the car in to the dealership or a good indy and have them determine the problem for you and give you an estimate of the cost of repair. At that point you can decide if you want them to carry out the repair or tackle it yourself.
I'm a little surprised that you have been unable to find this information as there are literally hundreds of posts about code issues on this forum alone. Did you try doing a search?
Hope that helps.