How to append image/video to dropzone area when upload using external link?

May i know how can i append the image/video uploaded by external url into dropzone area?

As what i know, i can retrieve file stored at server in such way

 myDropzone.displayExistingFile(mockFile, "https://i.picsum.photos/id/959/120/120.jpg", callback, crossOrigin, resizeThumbnail);

But is there a way to append the uploaded image or video to the dropzone?

Note: i am not using dropzone to upload, i have external feature allowed user to upload by url.