Install a NeoForge 21.8.24 ( MC 1.21.8 ) server through the Control Panel (Servers → Select your server → Game servers → Add Game Server → NeoForge 21.8.24 ( MC 1.21.8 ))
Great customer support! Decent service that they provide for the price and overall just a very user-friendly UI with plenty of tip videos/written explanations for noobs and veterans alike!