You can include videos on the opt-in & share widgets/pages you create using UpViral, which can be added inside the visual editor (when you are editing your opt-in or share page).
Here's how to add a video to your pages:
Step 1: Double click on text inside the editor to reveal the menu.
Step 2: Click on the video icon.
Step 3: Add in the URL of your video (e.g. YouTube video link).
In case you want to replace a current video with another video:
Step 1: Click on the video.
Step 2: Click on the "Replace" icon.
Step 3: Add in the new video URL.