Placed battery wrong.

Start by checking all the fuses. If all fuses are good, you pribably fried the ECM (computer )

Thank you. I'll start with your advice and let you know further.

Actually you probably fried a fusible link (or two). Fusible links are designed to burn out in order to protect the rest of the wire harness. Google what those are and where they are located for your make and model.

You could have fried every electronic circuit board not protected by reversing the polarity (+ to -). You can remove the radio and hook it up to a 12 volt source. It it's gone, probably most other systems are also.