Idk how to edit js and css code for a sticky nav

Can someone help me? This sticky menu is in the body coded but I want it in the nav code... Only I can't code JS to CSS.

For example and editing, I provided a JSFiddle link.

http://jsfiddle.net/x8z4snt5/1/

Here a piece of css code (For the full code press the link above):

     header {
     position: fixed;
     width: 100%;
     padding-top: 50px;
     background: transparent;
     transition: 0.7s all;
     z-index: 100;
     font-family: 'Montserrat', sans-serif;
}
 body.header-fixed header {
     position: fixed;
     top: 0;
     background-color: white;
     right: 0;
     padding: 10px;
     box-shadow: 0px -14px 29px #00000059;
     width: 100%;
     z-index: 2;
}
 header .inner {
     width: 100%;
     position: relative;
     margin: 0 auto;
}
 .logo {
     float: left;
     background-image: url('../images/logo-wit.png');
     background-size: cover;
     height: 50px;
     width: 210px;
     margin-top: 10px;
     margin-left: 100px;
}
 body.header-fixed .logo {
     background-image: url('../images/logo-zwart.png');
     margin-top: 15px;
}

I hope you guys can help me!

Martijn