If you're wanting to use your own picture instead of one that comes with DVD-Lab, go to the Assets window and right click in the white area. Click Import, change the entry in Files of Type to Image Files, and select the image file you want to use. Then you can drag and drop it onto the menu, and resize there if you want. If you want the image to be available for future use in DVD-Lab you can select the Images tab in the Assets window before you import, and it will keep a copy so you don't have to re-import every time you want to use it. You could also import into Backgrounds, but if you do that the image will fill the entire background of the menu and you can't resize.
