How to hook up external amplifiers?

I have a 98 Ford Explorer and I plan to buy four 6.5" component speakers for my doors. I was looking into JBL GTO638 s and want to adequately power them. What would I need and how do I hook it up? When I purchased the vehicle it already had 2 sets of speaker wire ran to the back. Could I hook the amp to these wires that run directly from the car battery and power my speakers with it? Thank you for sharing your knowledge.

Read more: How to hook up external amplifiers?