1)

Click on "Add Step"

2)

Select "Inline Step"

3)

You are in Capture mode, select an element to open creator panel

4)

Select an element

5)

Here, you can add or change step title and description 

6)

Opacity scale varies from 0 to 10.
Zero being the lightest and Ten being the darkest

Here, screen opacity is zero

7)

When the opacity is set to 4, the screen is slightly darker

8)

Click on "Save"