How to add a watermark on the video?

Click the Edit button, it will pop up a dialog box. In Watermark tab, there are two options: Text Watermark and Image Watermark.

Text Watermark: Type some texts as the text watermark.
Image Watermark: Import an image as the watermark. Adjust the slider to adjust the transparency of the image.

Click Delete button to delete the added watermark or click Font button to adjust the font, adjust transparency by setting the slider. To set the position of it, you can just drag it on the preview window.