How to make a custom widget based on “ink-blgs-widget”?

Hi,
I want to show a video instead of the blog image in the widget ink-blgs-widget. So I want to make my own instance of this widget, but how can I do this? I tried it like here
https://siteorigin.com/docs/widgets-bundle/getting-started/creating-a-widget/

But is does not work. Any documentation from your side how to set up own widgets based on your plugin?
Many thanks!