Add a custom field of type image to a news widget.
The following steps are given below
1. Add new custom field for News
2. Set its type to short text
3. Set “Interface widget for entering data” to Custom
4. In the custom textbox enter: Telerik.Sitefinity.Web.UI.Fields.ImageField
5. The image selector appears in the news publication view as expected and an image can be selected from local machine or image library
For more information check this, Add custom image field