Hey,
While you select the category of photograph to be submitted, you just need to set the category as 'Deviant Art Related' in the categories. There you will find DeviantId.Use that.
Later in the main page, you have to add a display widget which reads DevID. That widget will allow you to select one deviation from your deviations as Deviant id. But only out of those which have been submitted under the Deviant Id category.
Enjoy.