While the loop for the list is like a repeat region you will need to have the form elements within a repeat selection. You can apply this by selecting just the form elements to repeat, then select Server Behaviors > DataAssist > Repeat Selection.
The multiple insert works on a group of form elements that are repeated dynamically. The server behavior makes use of these repeated fields and must have them on the page in order to function. Once you have it setup correctly you will be able to add in the multiple insert and for the bindings you will specify the repeated form field for the corresponding column.