Using Waypoints Sticky Elements to fix elements to top of page upon scrolling in WordPress. http://sridharkatakam.com/using-waypoints-sticky-elements-fix-elements-top-page-upon-scrolling-wordpress/

functions.php

add_action( 'wp_enqueue_scripts', 'stick_elements' );
function stick_elements() {

	wp_enqueue_script( 'waypoints', get_stylesheet_directory_uri() . '/js/waypoints.min.js', array( 'jquery' ), '1.0.0' );
	wp_enqueue_script( 'waypoints-sticky', get_stylesheet_directory_uri() .'/js/waypoints-sticky.min.js' , array( 'waypoints' ), '1.0.0' );
	wp_enqueue_script( 'waypoints-sticky-init', get_stylesheet_directory_uri() .'/js/waypoints-sticky-init.js' , array( 'waypoints-sticky' ), '1.0.0' );

}

gistfile1.css

/* Sticky Tagline section at viewport widths 600px and above in Minimum Pro
---------------------------------------------------------------------------- */
@media only screen and (min-width: 600px) {

	.minimum .site-tagline.stuck {
		position: fixed;
		width: 100%;
		top: 62px;
		margin-top: 0;
	}

	.admin-bar .site-tagline.stuck {
		top: 90px;
	}

	.site-tagline.stuck {
		position: fixed;
		width: 100%;
		top: 62px;
		margin-top: 0;
	}

}

style.css

/* Sticky Primary Nav at viewport widths 600px and above
----------------------------------------------------------- */
@media only screen and (min-width: 600px) {

	.nav-primary.stuck {
		position: fixed;
		width: 100%;
		top: 0;
	}

	.admin-bar .nav-primary.stuck {
		top: 28px;
	}

}

waypoints-sticky-init.js

jQuery(document).ready(function($) {

	$('.nav-primary').waypoint('sticky');

});