You can use the wpc_publish_body filter to achieve this, e.g.
add_filter( 'wpdc_publish_body', function( $body, $remote_post_type, $post_id ) {
if ( 'create_post' === $remote_post_type ) {
$body['tags'] = array( 'tag1', 'tag2' );
}
return $body;
}, 10, 3);
2.4.5 adds post_id as a param to the filter to make the specific case of adding tags to posts of certain types easier.