To get the wiring diagram, you can check your owners manual. If you don't have the manual, go to the dealer website, they often have them there. You can also try this website...
Your local library has access to free online automotive repair information and resources, including wiring diagrams, for nearly all makes, models and years. Go to your library's website and look for...
Your question is too vague to be meaningful.
If you are looking for a SPECIFIC radio you should say that. Many times you can find diagrams online by visiting the manufacturer's...