as nobody told you, I will :
You need to put USBLoader_gx folder inside the /apps/ folder, not inside /wiiu/apps/ !
like said above, this loader can't be used to launch WiiU games.
There's no need to use a game launcher for wiiu games as games are installed directly and officially into the console or HDD.
There is a game loader called Loadiine, but it doesn't have network access (you can't play online), and not all games are working.
Though, you don't need a CFW at all.
You can launch USBLoaderGX directly from WiiU installed channel (no need to launch vWii mode first), but it will NOT load wiiU games. It's a Wii and Gamecube loader only.
there are two different methods to do it :
Method 1 :
WiiU WiiVC injector script.
1- install the wiiu channel with WUP installer
2- put USBLoaderGX in sd:/apps/usbloader_gx/ folder
with this method, you need to injects USBLoaderGX forwarder into a WiiU Wii virtual console channel
Cons: You need to create the channel yourself. It will launch USBLoaderGX directly, but USB will not work. This is useful if you want to launch Nintendont from USBLoaderGX interface. Only SD card works.
pros: advantage is that nintendont will work on the WiiU Gamepad.
Method 2 :
USBLoaderGX forwarder for WiiU.
1- install the wiiu channel with WUP installer
2- install the Wii forwarder channel on vWii with a WAD manager
3- put USBLoaderGX in sd:/apps/usbloader_gx/ folder
With this method, you need to install a homebrew wiiU channel forwarder on WiiU mode, and a Wii channel forwarder on vWii mode.
this forwarder will launch another forwarder located on vWii, which his turn will launch USBLoaderGX.
Cons: you don't have WiiU gamepad support in games.
Pros: you don't need to create the channel yourself. Everything is working (SD, USB, Wii, gamecube, nand, emuNAND, neek, cheats, settings, etc.)