Here's a guide how to add a related news item:
In your case, you need to add related media of type Image and access its properties in the template. To see the full list of properties of the Image item, please refer to Sitefinity API reference.
If you rather prefer a working sample, create a Dynamic content type with an image field. Sitefinity will auto-generate a widget with templates for it. Then go to Design -> Widget templates and have a look how your related data image field has been rendered in the the detail template for that widget.
I hope this helps,