Hi,
Follow the below steps.
1. Add one field for CC and one field BCC in the schema and UI.
2. Now go to Tools àData connections.
3. Click on Modify button for “main Submit” data connection.
4. Enter CC and BCC fields’ path in the Data connection wizard.
5. Click on Next, next and Finish buttons.
Now you can enter CC and BCC fields in the form and then you can able to send the mail.
You need to enter data in the "Title" field for Subject.