Push "Add Query" button to add SELECT-query filtering MS SQL data that will be migrated to MySQL server. See Using Queries article for the further information.
To edit table or query double click the corresponding item in "Selected tables" list box. If it is a table, dialog box appears to edit table attributes and to define custom type mapping. See Edit Table article for the further information. If selected item is a query, you will see dialog box to edit SQL-statement of the query.