How do I install Latex for MediaWiki?

I have MediaWiki installed and upgraded to 1.19.11.
I want to add Latex (Tex) markup support.

I have read the instructions here:

But I do not have a wikiInstallationDirectory/math directory. Are there updated instructions anywhere? I have verified that latex is installed on the server and updated my LocalSettings.php as indicated.

Plan: Happy Hosting - shared hosting

The instructions on the DreamHost wiki are out of date — the MediaWiki Math extension is no longer part of the core application, and must now be downloaded/installed separately.