Placement of leaderboard ad in Goliath

Hello, first timer here.
I recently added a leaderboard ad (It says “ADVERTISE HERE!” to the top of my website’s homepage using the theme Goliath. It looks like this:

I want to configure where this ad would go. For instance, I’d like it to be in the center top of the front page, below the title, not off to the right.

How do I do this?

I’ve already created the ad in Ad Rotate Pro, and I have a shortcode for it. I assume I need to place that shortcode in somewhere in the theme header section of the theme editor. If that’s the case, where should I put it? Below’s a screenshot:

This is my first time messing with the theme editor, so any insight for a beginner is welcome.