You do have the correct steps, but for an update page you will need to do one more thing. The forms that are built by DataAssist by default are defaulted to show the current value for a particular column, the information comes from the recordset on the page.
You can either just bind the recordset value to it's corresponding form element, or you can manually update the code to add in the binding from the recordset. If you bind the value through the bindings interface you will loose the value that is there by default from CSS Form Builder.
By default form builder sets the value of the form elements to the validated text in case there is an error on the form this will retain the values that were entered by the user. I think in your case though you would probably prefer to have the default values from the recordset show if there are any error when submitting the form.
Your update page is not updating the record correct? Can you confirm that the update server behavior is being triggered? It looks like the trigger is set to any form post, you should try updating this to be submit button pressed. If you still have trouble with it after updating the trigger you should print out the query by adding a new line just after what is currently on line 73. In this new line add this code:
This should force the update query to be printed to the screen and let you know what is going on with it. If you do not get the query to be printed then it indicates that the update is not being triggered. Please post back with your result.