Here is how to add to a presentation...
In the Google Slide – click on INSERT.
When the drop-down opens, choose SHAPE and then choose CALLOUTS.
The CALLOUTS will have shapes in them and the row at the bottom is the ones you want to choose.
Once you choose it, just go to the slide you want and click in it and the CALLOUT will appear. Click inside the CALLOUT and you can add text.
We now have an app in our Google Suite we can use to create Audio in our presentations. You can find it in your email on the top right of the screen. Download everything and watch this video. Enjoy!
In Google Slides, choose the Add On tab. When that opens, you should see the add on's that you have access to. It is recommended you watch the video on how to use SLIDO.