where it tells me to change the backround image, I type the new link in and my preview box remains white. is this supposed to happen?
An image should fill in the entire jumbotron div's background. If you are seeing no image then you might have the URL wrong or there might be an problem with the syntax somewhere in your CSS file.
You can post your code here if you'd like someone to help spot the problem.
How to post code in this forum.