Well overlays are important for any good story so learning how to use them is something you need to learn.
Basics -
How to add an overlay to the start of a scene?
INT. BACKGROUND with OVERLAYNAME
How to add it in to the middle of a scene?
@overlay OVERLAYNAME create
@overlay OVERLAYNAME opacity 1
How to move and scale an overlay?
moving and scaling an overlay is like spot directing a character.
Once you have the code copy it into your script
It can look like this -
or like this
if you need help with overlays I would recommend watching Episode Notes or Joseph Evans videos