Here is a test site for you:
http://luo200.discover-wp.com/cred-form-to-submit-information-of-two-custom-post-types/
user/pass: xgren/111111
In section "Groups"
1) you can click "Add" button to add new group
click "Show Popular" you can choose exists groups
2) after submit, all data will be saved into database
CRED form:
http://luo200.discover-wp.com/wp-admin/post.php?post=17&action=edit&message=4