Step 1: Setting up Cemu
Download the lastest (or whatever version you like) Cemu version from Cemu.info. After that, extract the folder that was downloaded to C:\Wii U Emulation (This name is required for it to work.). After which, you double-click the Cemu.exe file (you may have to go through a few folders to get to the .exe), and go through the main setup process. I do not endorse pirating games or system files, since you need to extract them from an REAL Wii U.
Step 2: Purchasing the required things
You’ll need a BackBone Pro, TV, HDMI Cable, and a mobile phone (Android and iOS are supported).
Step 3: Downloading the required apps.
You will need to download the official BackBone app for the controller to even get set up, Steam on your PC, and Steam Link on your phone.
Step 4: Connecting the dots
When you connect the BackBone Pro with your phone, you will see a screen saying to download the official app. Download the app and open it. Go through the initial setup process, and, put the BackBone and your phone away, as we will make use of them later. Download the official Steam software from https://store.steampowered.com/about/, and make an account. Next, download Steam Link on your phone (Make sure your PC is connected to the same wifi as your phone) and connect to your PC. You will see Steam in Big Picture mode. Press the windows key and right click the steam application. You will see Exit Big Picture mode. Click on it. Now Steam will be a Window. Minimize it. Now plug your HDMI into your TV. And plug in the HDMI Cable into the HDMI port on your PC (and if you don’t have one, use an adapter.). Now, open settings, and click Display, and you’ll see something like a screen saying 2|1 on it. Extend the display. Now, open Cemu and drag the window to your TV. Click Tools in Cemu, and click Seperate Gamepad View. Move the Gamepad View to your PC. Now get your backbone pro. On the bottom, there should be a tiny button. Hold it. Pair the BackBone Pro to your PC, and in Cemu, click Options, Input Options, and on controller one, map everything to Wii U Gamepad. I will link how to pair a controller with Cemu and map it right here https://www.youtube.com/watch?v=Cyaf3tB3UIA
Now, go in the backbone app, and click Control Wireless Device. Then, for the final step, Move your cursor to the computer. Steam Link should be showing the Gamepad view. Now launch any Wii U game YOU own (I do not endorse piracy, but you likely do have some Wii U games, right?), and you can play. I hope this helped you all! I am not a fan of reddit, so this post might not get viewed as much as on Reddit.