To download the images from the URLs you have stored in the DB, you could use a WebClient. Further, you should load the downloaded image data and set the corresponding property in the view model to which the RadImageEditor's Image property is bound.
For your convenience, I've created a small sample project which illustrates the described approach above. You can find it attached.
I hope this helps.
If you need further assistance, please get back to us again.
Regards,
Todor
Telerik
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