Customize Zen Cart Buy Now Page

Hello everyone! This is nothing big but I can't figure out how to do it.? I want to format the Buy Now page on a Zen Cart template. It should all be plain CSS.? The project includes:? Moving the main picture to the center and enlarging it a little bit. Move the description to the center as well, underneath the main picture. Change the "Add to Cart" button? And maybe add one more picture.