How to create/apply jquery scrollup menu fix

Hi, how can I create a jquery scroll-up menu fix? I have fixed menu in place in my Divi powered multisite but it shortens the view area hence, looking for a solution to make the fixed menu slide up to the top of the site while scroling and fixed. How can you help me achieve this?

Screenshot link: http://awesomescreenshot.com/0da45j1f3c