Data Assist and Image re sizer will not handle the image upload, for that you will need to use the File Manipulation -> File Upload functions included with Universal Email or with CSS Form Builder.
The File Upload behavior will upload the file to the specified location on the server, you can then set data assist to store the file name in your database.
see the "How to apply Digital File Pro to DataAssist Insert and Update pages" tutorial on the data assist support page:
dataassist/
the "Displaying your upload images on DataAssist pages" section walks through showing the uploaded images on your pages, you can apply the Image resizer behavior to the pages that display the images to dynamically size them to the height and width specified.
