Editing Custom Page Templates in twenty eleven child

Newb working with twenty-eleven child theme. Created a custom page template successfully and it shows up in my “choose templates” menu.

So to start editing: 1. the custom page’s header (no header img, transparent bg behind site title and nav, etc.), and 2. the body (content area only as big as entered text, etc.), I’m confused over where to put various customizations for the custom page template. Some seem like they belong in style.css, while others may belong in the other child theme php files (custom page template, header, function). I couldn’t find a clear answer in codex.

If anyone could offer some pointers or direct me to a good thread or tutorial (most just stop after “creating a new page template” but don’t specify exactly where diff types of edits get done), I’d be much obliged.

Thanks!!