Find a web host or create your own
Visit a website hosting it, like
http://dlae.life/,
http://wiiu.insanenutter.com,
http://www.wiiubru.com/x or
http://u.drg.li/
or host the
sources on your computer.
If it's on your computer, you need python installed, and launch "startServer.bat" on windows, or use any other webserver you want.
Run the browser hack on WiiU
Clear your browser's data, launch the browser again.
Open the server's URL in your browser, or your computer's IP if you are hosting it yourself.
select Exploit
If it freezes, shutdown and try this step again. It can be quick if you are lucky, or taking hours of retries...
If it works, use that opportunity to install haxchi, it will be more stable.