How to add coloured block behind the header?

Hi all,

          how do I add a coloured box behind header? Because right now the header is just text and when I scroll down it overlaps with other things in my webpage. 

Example: *image below*

Thank you in advance.  

Can you share site url? We can help easier.

Hi, 

Thank you so much for replying. Somehow, its okay now, not sure how. But thank yo so much.