Hi there,
First, the image needs to be a PNG with a transparent background.
Then, it needs to be placed inside a container, inside of the container below the navigation.
So it would look like this:
<div class="my-balloons">
<img src="..." alt="" />
</div>
That would go below your navigation.
Then, you simply need to add some negative margin to the top of that container, so it would become:
<div class="my-balloons" style="margin-top:-10px;">
<img src="..." alt="" />
</div>
Then you would adjust the 10px to your liking.