Normal Install Method
This will reset your dimension(s) - you should only do this on a new world, or if you're okay with resetting! Pick your favorite server software (Fabric, Paper, etc) since this method will work on all of them, whether you're using a hosting service or not.
1. If using datapacks (ends in .zip), put them all in the world/datapacks folder. If using mods (ends in .jar), put them all in the mods folder.
2. Start your server, wait for it to load, then stop it.
3a. [Terralith/Continents] Inside the world folder, delete the entire region folder, and nothing else.
3b. [Incendium/Amplified Nether] Inside the nether folder, delete only the region folder, and nothing else. On Spigot/Paper, the nether folder is world_nether/DIM-1, and it's world/DIM-1 on Fabric/Vanilla.
3c. [Nullscape] Inside the end folder, delete only the region folder, and nothing else. On Spigot/Paper, the end folder is world_the_end/DIM1, and it's world/DIM1 on Fabric/Vanilla.
4. Start your server again, and enjoy!
Note: *You can add Structory to an already generated world - the structures will only generate in new chunks, though.