Constructor Theme – Ad Space Help

I need to add ad space above or below my header, I was previously using swift which was great but I felt it looked to cluttered after a while.. Constructor is great and I love how much you can customise but it’s missing this very basic option and I have very little CSS knowledge so no matter what thread I read I just can’t understand how to add it via coding. Can anyone offer a solution or really dumb it down for me where to put my html ad code?

THANKS IN ADVANCE!