I don’t think we have official support or guides for those engines/APIs yet. But we happy if you could share your experiences.
Generally CrateDB exposes a Postgres compatible Interface on the postgres Port 5432. So you can connect to CrateDB pretty similiar as to a native Postgres database. If your are running CrateDB on your local machine you may use the user crate without password. If you are using a cloud instance, be sure to activate TLS/SSL in the API/engine and use your credentials to login.
Also CrateDB has an http-endpoint cratehost:4200/_sql that can be used to send SQL requests directly via http(s).