Well first you need to pick a host that you like. (See if you can get a code from a youtuber's video. They often have deals).
Just google minecraft server hosting.
The other option is minecraft realms
Then you need to build the stuff for your server.
And finally you invite people.
Voila that was my bootleg guide to server creation.
(Oh I also recommend starting a Patreon or something to help offset costs)