Вы можете использовать функцию wordpress wp_insert_post
// Create post object
$my_post = array(
'post_title' => 'My post',
'post_content' => 'This is my post.',
'post_status' => 'publish',
'post_author' => 1,
'post_category' => array(8,39)
);
// Insert the post into the database
wp_insert_post( $my_post );