In 4.12, ART is now an optional checkbox on install, that defaults to off (thanks engine guys! :p)
If you’ve already installed the engine, you can still access that page on the launcher using the small dropdown arrow beside the engine version to access those install options.
From there, grab the dropbox files and paste over your local files. The files in dropbox are not the complete package, just updated scripts.
Furthermore, you may want to consider moving the tools out of the engine directory. It doesn’t matter where the MayaTools folder is located. From there, you can update your settings in the epic games menu to path to the new tools location, or delete the mayaTools.txt as shown here: