Thread pool documentation lacks how to enable it

In the thread pool documentation it lacks how to enable it:
https://mariadb.com/kb/en/mariadb/thread-pool-in-mariadb/

In the old documentation there is such note, in the first paragraph of the entry:
https://mariadb.com/kb/en/mariadb/thread-pool-in-mariadb-51-53/

Please add the simple howto how to enable it in the first link as well.