You can find the Torn-edge effect in the Toolbox under the Objects tab in the Object effects section.

With the Torn-edge effect, you can add irregular edges to photos, videos, shapes, and text, similar to the edges of torn paper. To add torn edges to an object, place it in the effect.

1 Insert Torn-edge effect

Drag the Torn-edge effect from the Toolbox into the Timeline. In the Timeline, you will now see a colored box. Insert your image or video here. If there are already images or videos in the Timeline, you can also drag the effect directly onto them.

2. Settings for the Torn-edge effect

In the Properties area, you can set specifications for the appearance of the torn edges.
 
Use Width and Height to specify how large the content will be displayed in the effect. The Size affects how much of the border color is visible.
A low Roughness value results in soft-edged tears, while a higher value makes the edges appear pixelated.
With low Variation, you get straight edges and even spacing between the content and the color border; with higher Variation values, the edges appear in more irregular shapes.
 
You can adjust the border color using the color picker. If you set a transparent color, you will only see an irregular edge without a colored border.