Header Graphic not resizing…

New too WordPress but getting the hang of it…

However ran into a issue with the Sela template.

The main header is not resizing and I’m just not sure where to put the correct CSS to do so.
As you can see from the URL below the other graphics (images) are resizing.
http://test.capitalcitydoulaservices.com/doula-trainings/

background-image: url(/wp-content/uploads/2015/02/NewHeader_brown.png);

help,

Mark