Where can I find "Plugin Directory"?

I read from a post that you can install plugin to automatically download subtitles. But I cannot find the place or tag called “Plugin Directory”.
Could anyone tell me where it is or how to install plugin for plex?

https://support.plex.tv/articles/201106098-how-do-i-find-the-plug-ins-folder/

@trudge said:
https://support.plex.tv/articles/201106098-how-do-i-find-the-plug-ins-folder/

To add to this because some have custom install locations.
You can get to the plugins by right-clicking PMS and selecting Open Plug-ins Folder.

or you just use opensubtitles.org (Settings > Server > Agents > [Movies or TV Shows] > [applicable agents] > check: opensubtitles.org; you might require a login).