image within Header

Few questions about this widget/header banner?

1. How do I extend the header throughout the full row (width) of screen? (exactly like the green menu bar on top)

2. When I have it in the footer, and full width row, the image sits outside the widget- How do I make sure this doesn’t happen when I extend the header widget to full row?

3. I tried adding background- white but that isn’t doing anything; how do I make the color white?

http://www.localgreeneats.com/category/blog/

Thank you