VYPER 2.0 METHOD
1.) Go to the Launch tab
2.) Go to step 2 Meta Tags and scroll down until you see Social Share Image. This is where you can upload or copy/paste a URL
VYPER 1.0 METHOD
Want to change the default preview image when a link is shared?
If you're editing the contest, simply go to the design step (on the bottom navigation).
Then click social media images & settings on the left-navigation.
If that doesn't fix things, Facebook may have cached your image.
Use the Facebook debugger to uncache your image.
Alternatively, Twitter has a card validator as well.