No !
having the .wad file on SD card is NOT enough!
You have to use a WAD manager (YAWMM for example, the one I linked to you) to EXTRACT (install) the .wad's content and copy the content into your console's memory.
that internal data located ON YOUR CONSOLE (not the SD) will be represented as a channel installed on your system menu.
once installed INTO your console (and not just copied on your SD), then the wad file on your SD card is not needed or used anymore. you can delete the wad and the wad manager AFTER you successfully installed it as a channel on your home menu.
the wad file is like a zip on computer, but a zip for the wii or vWii.
that wad file contains multiple files insides and information where to install it into the console (the channel's banner, the channel's name, the channel's executable, etc.)
launch YAWMM, select the wad located in your wad folder and choose "install" to .. well .. install it.
If you have " USB Loader GX-UNEO_Forwarder_5_1_AHBPROT.wad" on your SD card ....
That's WRONG !!!
you are in the WiiU section of the forum, so I suppose you are using a WiiU, so you want the "vWii" version ! TotalInsanity also supposed you were using vWii, as he asked me if there were a compatible vWii version to help you.
if you install the Wii version on vWii ... no wonder it just return to the menu and doesn't work.