You can add default values to your columns:
- while creating the table, by filling the "default" textbox for the given column
- while adding/modifying a column from an existing table, by filling the "devault value or binding" textbox
Generated scripts are not editable.
You can run your own script from the Tools/New query tools.
Also, i recommend you to read the Quick Start Guide:
http://livedemo.mylittleadmin.com/livedemo/quick%20start%20guide.pdf