how to input the security code for 97 camry

My friend has a 97 camry. He replaced the battery recently and the audio system locked up afterwards. He has the security code. But he doesn't have the owner's manual, so he doesn't know how to input the code. Does anyone know the procedure? Thank you very much!

I'm pretty sure you could contact your local Toyota dealership, and they should give the instructions to you over the phone.