to accomplish this in Data Assist, you need to manually add the Data Assist insert record behavior to your page.
It sounds like you already have the form set up and the upload behavior is working, if you look on the bindings panel, expand the "WA Uploaded File(File Field)" binding group (where File Field is the name of the file field in your form).
This binding group will contain bindings for the status, and server file extension, server file name. If you look further down the list, he binding begin to repeat. there will be section of bindings specific to the file created in the /images folder, and then another section of bindings specific to the file created in the /images_thumbs folder. each of those section will have a server file name bindings.
to add the insert behavior, go to the Server Behaviors panel and click the plus button. Select WebAssist -> DataAssist -> Insert -> Insert Single Record
on the first tab, you will select the table to insert the form data to, on the second tab, you will bind each column to the form.
select each column, then click the lightning bolt icon next to value and select the corresponding form element from the dynamic data bindings.
For the Main image column, expand WA Uploaded File(File Field)" binding group and select the Server File Name variable from the section for the /images folder.
for the thumbnail column, select the Server File Name variable from the section for the /images_thumbs folder.
A better alternative though, is to use Image Resizer. Instead of resizing the image using the File Upload and creating 2 copies, you would upload one large image and stoere that file name in the table. then use image resizer to add the thumbnail to your page.
The advantage to using Image Resizer is that it dynamically creates a new image for you. if you decided down the road that instead of 120X90 for the thumbnails, you want to use 120X120, you only need to change the image dimension on the page, and image resizer will automaticly recreate the thumbnails for you.
