How do you add a blur box in iMovie?

Based on the provided reference, to add a blur in iMovie, you adjust the sharpness:

1. Go to the adjust settings in iMovie.
2. Find the color adjustment options.
3. Locate the "sharpness" setting.
4. Drag the sharpness slider to the left to decrease sharpness and create a blur effect.
5. Save the changes.
6. Repeat the steps if more blur is needed.