How do I set an element to be Full Width?

Many Elements have the ability to be set Fit to Width in the Design Panel. 

If the element has the ability to be set 100% you will see the Fit To Width option located just above the Arrange settings within the Design Panel. 

Check the box - to set the element to fill the entire browser width. 

You will automatically see the element fill the entire width of the Canvas. The grey areas on either side will remain grey for your working space.