The Twitter plugin is an "official plugin", and this installed in the Node.js folder that TW is downloaded to. You will simply need to edit the wiki's `
tiddlywiki.info` file and include it as "tiddlywiki/twitter" in the plugins array.
Non-official plugins will need to be downloaded and placed within each wiki' folder's "plugins" folder, or in a central folder that you then set the "TIDDLYWIKI_PLUGIN_PATH" environment variable to before starting TW.
Best,
Joshua Fontany