I assume you are using windows. And if yes, you can follow the guide provided by Wiki of rA. Link: https://github.com/rathena/rathena/wiki/Install-on-Windows
For a game client to work you need base file such as client files. By this, you need to download kRO files. (disregard the ragexe in the kRO clients since they are not unpacked).
There's a guide that gives information about it and I think its on the Development News Section. To make your server public, you need to do some routing to the net. If you want to use your own desktop you need to open ports/NATS/port forwarding and etc. (Not familiar with this) or just rent a VPS.