If I want InSim to control a multiplayer game, without running an LFS instance myself, how should I enable this and how do I know what IP should my app connect to?
When you rent or create a free server, you can always see the IP which you should connect InSim to, on the https://www.lfs.net/hosting/admin page. You will have to whitelist the IP from which the InSim app will try to connect, though (in server settings on the same page).