Remove the gap between the Menu and the contents of Page

if you go to www.boudetfrance.com you will see a VANTAGE themed website.

I would like to put a slider either ABOVE the menu or DIRECTLY BELOW the menu.

Whenever I try and do this via the siteorgin web page builder i get a gap between the menu and what will be my slider.

http://www.boudetfrance.com/wp-content/uploads/2016/06/gap.png

Can anyone advise on what i should do to get rid of that gap or place a slider/image/etc directly ABOVE the menu or BELOW the menu.

Thanks