Install a NeoForge 21.0.163 (MC 1.21.0 ) server through the Control Panel (Servers → Select your server → Game servers → Add Game Server → NeoForge 21.0.163 (MC 1.21.0 ))
This is my first time running a server and its pretty easy to figure out. Lots of helpful videos and quick responses after submitting a ticket for assistance. So far I'm enjoying it.