Part 1 - setting LFS free server:
From LFS main menu: Multiplayer/Start new host
Set your server name and admin password, remember it, and press go
When logged to lfs.net open
https://www.lfs.net/hosting/admin and click your host name, what should interest you is Host IP InSim port and Access control page, open it
Place your IP address in Allow IP addresses to the InSim port textbox, if you don't know your IP go to Activity tab and it will show next to your name.
Part 2 - configuring Airio
Open Airio.con.1.txt with text editor and change values
HostAddr=Host IP here
HostPort=InSim port here
HostPass=Your admin password here
Run Airio.exe
When you have basics done now you can configure Airio to your liking (maybe at this stage make backup so your progress isn't lost). As mentioned free servers change IP and ports every time so either don't leave your server or consider renting one.