background image like in the construction demo

Hello-sorry, I’m such a newbie at this. I want to create a box similar to the construction demo “why us” box on the front page. I want to use grid paper or possibly my own picture but I want it to be dimmed like in the construction demo. I created a color section and added a photo in the section background but the photo doesn’t stretch all the way across plus it is not dimmed. Thank you!