Requirements:

How to use Annotation:

The Presenter will start sharing their screen. The person presenting will see the button to enable to disable Annotation:

Enable

All others may write on the screen by choosing the Pencil Icon. You will see the icon on the lower right-hand corner:
Pencil

Once you click Got It you will be able to choose a color to write with by clicking the pencil:
Color

When you write on the screen, it will show your name to indicate who is writing at that time:

Name

The annotation will automatically disappear within approximately 5 seconds.

Gif

For troubleshooting, check the following article Troubleshooting FAQ - Screen Annotation