Download the NeoForge installer from https://neoforged.net/ and install the NeoForge server inside this directory. (You will have to run the installer to install it...)

Optionally adjust the RAM usage in the user_jmv_args.txt in the last line (-Xmx6G).
After that you can use the run.sh (Linux) or run.bat (Windows) to start the server.

Make sure to use /chunky to pregenerate the world for an optimal experience!

Happy floating!