Hey,
sorry that no one answered your question. The point is:
There really is no big tutorials series on this subject yet, but:
You can have a look at the ShooterGame Project. It is using the OnlineSubsystem. You just need to know that you aren’t really using SteamFunction but the Engine is “transforming” them if you have Steam enabled. So if you have Steam Enable and you have your “OnlineSubsystem” variable, you can call everything you want. Still there are some things that are unique to the Steam subsystem.
Have a look at the ShooterGame Example avaiable in the Launcher. They use the OnlineSubsystem with OnlineSessions etc which is running with and without Steam depending on Steam being available or not.
To get steam into your project have a look at this:
This should help you getting started.