WIX STUDIO - development of additional iframe code

Good morning. I am building a website in WIX STUDIO. The site will sell access to video streaming via restream (iframe). I need a code that will allow the user to display a graphic file transparently on the broadcast stream.

1. The user will purchase access through pricing plans (configured).

2. The user can choose a file from among self-added files (pdf, png, jpg, webp) or those added by the site administrator to the user's account. Each user has access to their files, files assigned to the user's account. Only the user sees the files.

3. The level of displayed transparency to be agreed upon. One for all files and users.