starbound multiplayer

First, I think you have to port forward, not sure though.

Click server in the launcher.

You'll need to open port 21025 on UDP and TCP for your computer, then just launch Starbound server from the laucher, and to connect, just put your computer IP (this will be 192.xxx.xxx.xxx form) and if you want someone to go on your server, just give him your internet IP, which can be found on this website : http://whatismyipaddress.com/