Expand width of header navigation

Hi, is it possible to expand the width of the header navigation to fit 100% of the width of the screen in desktop view? Right now, I need to change the entire background colour of the navigation menu. Except that the menu container seem to stop part way. Here is an example of what it looks like now, followed by what I am trying to achieve. Change from: To: Note that I already tried adding "width: 100%" to main-navigation, but that didn't work. For what I did with the background colour, I made this change:

.home .main-navigation {
background: #280014;
}