You haven't posted any code for others to look at. However, the basic way to get a background image to fill the element it's applied to is to use the background-size property, and set its value to cover.
By the way, this forum is dedicated to helping people with the Getting Started video tutorial for Dreamweaver CC. For general questions about Dreamweaver, please use the main Dreamweaver forum.
Hummm, that's odd. I copied the code in there. Oh well, sorry for posting in the wrong forum and thank you