Here is a video demonstrating how to create a simple Sitefinity MVC Hello World Widget;
and a direct documentation link on how to
Create MVC-based Sitefinity widgets
Regarding your screenshot with the error, I do not see the relevance to the issue or where this could come from.
Please observe the demo video and the documentation as mentioned above.
I hope the above information helps. Otherwise please provide the steps you took to accomplish this.
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