Drag the image that you want to use as the background to the timeline.
Select the Crop tool and then select Crop to Fill. Adjust the frame for the image as needed.
Drag the video with the green screen to the track above the background image.
With the green screen clip selected, click the Overlay tool and then select Green/Blue Screen.
You should now see your video overlayed with the background image. If you don't, you may need to extend the length of the background image. To do this, place your cursor toward the end of the clip and then drag right.
