According to your update it seems that you have got the text area in place on the insert and update pages correct? If you have added the text area and have the column in your db table then you just need to edit the insert server behavior and the update server behaviors.
To do this start with the insert, double click on it from the server behaviors tab. In here just go to the step where it lists the columns in your table, find your new column and select it. For the value use the lightning bolt icon to set the value to your new text area input in the form. Then just finish and save the page, that is all for the insert.
Next on the update page you just first select your new text area, then in the property inspector for the value use the lightning bolt, expand the recordset and make sure to select the new column from your table. Once you have done that part you can just update the update server behavior the same way that you did the insert, no different.
Please give this a try and let us know if you have any further troubles with it.