1. Let's turn your slides into a canvas. Click the "Slideshow" button to enter presentation mode.
2. Now, you're presenting. Move your mouse and a toolbar will appear. Click on it.
3. Click "Turn on the pen" to reveal your drawing options.
4. Go draw, circle, or underline anything you want to emphasize. Your audience will thank you.
5. That's it! By following these steps you can draw freely in Google Slides during your presentation.