1.- Download "SDCafiine 1.4", copy the wiiu folder to the root of your sdcard.
2.- Now make a folder on your sdcard (not inside the wiiu folder, on the root.) Name it sdcafiine, with no spaces or commas. Inside of sdcafiine you will need to create a folder that is named depending on region:
0005000010180500 - JAP 0005000010180600 - USA 0005000010180700 - EUR
3.- Copy your specified region titleID number and name the folder inside sdcafiine it. Open it and create a folder named content (should be sdcafiine/gameIDnumber/content), and install mods from here by placing them in the spot they should be according to said README of the mod (for example, skins for Captain Toad should go in content > ObjectData >).
4.- Now put your SDCard in your Wii U, turn on the console and run Homebrew Launcher and run SDCafiine 1.4.
5.- Boot up Captain Toad: Treasure Treacker after loading SDCaffiine. Your mods should load.