Board Thread:LotR Mod Technical Support/@comment-26184570-20180906140429/@comment-33185350-20180906140648

Download the mod from the home page of this wiki. Then click “go to folder...” in the menu for Finder, and I think you have to type in this into the popup window: ~/Library/Application Support/minecraft/mods

Switch out the .jar file for the new one you just downloaded, and you should be good to go.