Sticky header/menu for Radcliff

I’m currently building a site with the Radcliffe theme, however i’d prefer to have the header and menu as fixed in place so it’s always on the page when scrolling. I’ve tried a number of different options but the closest i’ve come left me without my chosen logo in top left and without the white background.

I’m new to WordPress and CSS & HTML so it’s mostly guess work at this point, any help would be appreciated.