Extract "version.dll" from that zip into the Balatro game directory. (Right click on Balatro in Steam, click Manage > Browse local files)
It is quite possible Windows Defender will label version.dll as a virus as it is Love2D injector and thus could be used for arbitrary code execution. That's the point, lol. If this happens do the following:
3.1. Open Settings > Windows Security > Virus & threat protection
3.2. Under "Virus & threat protection settings" click "Manage Settings"
3.3. Scroll down to "Exclusions" and click "Add or remove exclusions"
3.4. Add an exclusion > Folder: Add your Balatro game folder.
3.5. Put version.dll back in the folder again.
Open explorer and type "%AppData%/Balatro" into the address bar, then press enter
Create a new folder named "Mods"
Extract the "Steamodded-main" folder from the zip into the Mods folder you created, so you have .../Balatro/Mods/Steamodded-main/". This should have "steammodded_injector.py" and "lovely.toml" and a bunch of other files and folders inside it.
Run Balatro. In the top right corner, it should say the game version (1.0.1g-FULL as of writing) followed by the version of Steamodded (i'm using 0.9.8-STEAMODDED for personal reasons, it will say a different version if you're using the alpha). If that's there, you're good to go! Drop mod folders into that "Mods" folder next to Steamodded-main. Such that:
.../Balatro/Mods
/Balagay
/Reverie
/Steamodded-main
etc.