In the success part of your code, you can build an array representing a post, and use wp_insert_post as such :
Example
$mypost = array(
'post_title' => 'My Title',
'post_type' => 'page'
//... add other fields according to your form
);
$mypost_id = wp_insert_post( $mypost ); //Returns new post id on success
Any field you don’t specify will be filled by WordPress automatically.
EDIT
For custom fields, see add_post_meta :
$mypost_id = wp_insert_post( $mypost ); //SEE ABOVE
$meta_key = 'your-new-field-name';
$meta_value="your-form-value";
$unique = true; // or false
add_post_meta( $mypost_id, $meta_key, $value, $unique );
Source : wp_insert_post