Hello, there are a couple of things that you need before you can host your own server to everyone.
Check if you have a public IP or static IP - this is very important as you won't be able to host a server if you have NATed IP address.
Check if these ports 5121, 6121, and 6900 are open on your end. (You may search for guide on google on how to check these)
If you don't have a public IP, you will definitely need a VPS to host your server. (There's a topic here somewhere in rAthena of the list of recommended VPS) >> Take note that this will cost you some $$$
If you're just planning to setup a server to play with your friends, you may use Hamachi or ZeroTier One. These will enable you to setup a virtual network that your friends can connect to. (This is not recommended if you're planning on setting up a full time private server)