1
Move your cursor to the desired position on the timeline where you want to
add a callout, then navigate to the Elements option on the left menu.

2
Click on Callout. 

3
Adjust the position of the callout rectangle that appears.

4
Click on the element to access the callout settings. Modify the stroke
color, stroke width, background color, border radius, and scale factor as
per your requirements. 

5
In the animation section, adjust the draw time and transition time.
