Run the .exe file on Windows, or run java -jar ~/Downloads/fabric-installer-X.X.X.jar on the terminal for Linux users, select the latest version and install it
3 - Make sure you have a .minecraft/mods folder to put at least the mods listed bellow
Now just clone the luma-mix21 repo, move it to the .minecraft/resourcepacks folder and you are ready to enjoy Skyblock with the best features and the best custom textures from this amazing community :D