Under the driver's seat.Find a two socket, light blue plug and jumper the contacts.Turn car on and watch the check ngine light blink in long or short blinks and write the code down. A long blink is two seconds and a short blink is one second. The pattern will blink a serries, pause and blink another series. Those are the first and second numbers of the trouble code. It could make a sinle digit code where it keeps repeating the same pattern of short blinks with a two second pause between. The long blinks signify tens; one long= 10, two longs=20,etc.
See if your local parts store sells these OB I kits, containing the jumper probe and handbook.
If you want to reset the computer, remove the clock fuse