To create interactive overlays go to Audience Events, and then click on interaction
Once you are there, click on New Overlay
All your saved overlays will be displayed here, so you can later on go back and edit them.
Your next step is to fill in all necessary details for your overlay
You can specify your start and end time, or you can also check the box to show overlay at the end.
When you go to Overlay Styles you'll have a change to edit your overlay's appearance
Changing the style from "pop up display" to "overlay display" will make your overlay look more like Annotation.