Hi there,

I assume you're referring to the stage of DVD menu creation for your movie project. Just right-click on the thumbnail representing the movie in the DVD menu preview screen and a small context menu will open. Bring up the "Properties" option. Here you will find a position slide that enables you to basically use any frame of your video as the thumbnail image. Also, there's an option to browse for and use some external image file that is saved on your hard drive instead of a frame from the video footage.

I hope this helps!