Place navbar under jumbotron and fixed at the top when scrolling

I’d like the jumbotron to be above the navbar, but for the navbar to stay fixed at the top of the screen when scrolling down. For the life of me, I can’t figure it out. Any advice? Please see my code below:

looks like you need to add Bootstrap’s JS file

Thanks, I think I have added it at the bottom of the page and JS pane but to no avail.