Download Instructions: Download the Enderman Mod zip file. Extract the zip file. Drag the .pak file into your mods folder in your Minecraft Dungeons files. Don't know where they are or how to get mods? Look here! Windows store version: DokuStash (dokucraft.co.uk) Launcher version: DokuStash (dokucraft.co.uk)
After that's done, run the game in the files. Running the game via the windows store or launcher will delete all mods. Have fun!