The optins and social sharing in Vivid use Bloom and Monarch. In your download package you will find a bloom-settings.json and monarch-settings.json file.
The files need to imported into their respective plugins. You can find more information on using Bloom & Monarch below
Bloom Documentation: https://www.elegantthemes.com/documentation/bloom/overview/
Monarch Documentation: https://www.elegantthemes.com/documentation/monarch/overview-monarch/
If you add Vivid to an existing site usin Bloom, your form ID numbers will be different and therefore the forms may not show. Check the ID numbers of your forms correspond with the ID numbers in Vivid.
To change the 'Share this post' image next to the Monarch sidebar, find the following section of CSS in the stylesheet and change the includes/images/share.png path to the URL of an image from your media library.