get https://www.virustotal.com/ui/widget/html/
This endpoint returns the actual HTML content of the widget report for a given observable. It is a URL that will have been previously returned by a call to the /widget/url endpoint. It does not require authentication but it is only valid for three days. This endpoint will be typically called from your application's front-end/client-side, as a result of embedding it in an iframe.
You might find the VT Augment client library helpful when building the flow to display the widget in your own product. Its usage is not mandatory, a couple of lines of JavaScript will also do the job.