Need help to add a space [After Post]

Hello, can you guys help me adding a white space (margin) between the post and the ad? I tried myself using the “Preview” but it doesn’t seem to be working (edited both top margin/padding), ad always sticky to the posts, however it is working for the bottom margin/padding!

This is a picture showing what I’m talking about:
https://oi64.tinypic.com/kahcpg.jpg