Once you have opened Marvin and loaded your background image, go to the "Control Panel" on the left hand side of the page, under the "Multimedia tab", click the "Background Size" button.

The "Command Panel" on the bottom of the window has now changed to the "Background Size" menu.
Modify “Width” to 800px and "Height" to 600px
Choose to warp the image or keep the image aspect ratio. Images can be warped (squashed or stretched) by modifying the image size, while leaving the "Lock Aspect Ratio" checkbox unchecked. When "Lock Aspect Ratio" is checked, image sizes will be changed while retaining correct image proportions.
Set your new "background size" to 800px width and 600px height. Your new background settings may be previewed by clicking "Preview". If you are happy with the changes, apply them by clicking "Change Size". Alternatively you may reset the background size and undo any changes by clicking "Reset".
Using Marvin, create your movie. If you are new to Marvin you can download the Quickstart Guide.
Export your movie from Marvin
Once your movie is completed, go to the menu bar at the top of the page and click on 'generate' and then click 'export video'.

Select where to save your movie and give it a name.
Change the frame rate to 25fps and choose an audio capture source then click ok.
