Steam Matchmaking ShooterGame Example, where to start

So I recently begun work on a project which is going to need Matchmaking. I was wondering where I should start looking in the ShooterGame example for the functions which are used for connecting to a match, finding a match, and hosting a match. The best class in the project that I found was the ShooterGameSession.cpp file. However, I thought that GameSession extends from GameMode. The reason why I bring this up is because I read this “The session interface is created and owned by the OnlineSubsystem. This means it only exists on the server.” So does this mean that if I put my HostGame and JoinGame functions into the GameSession file it will not be accessible to players?

I have been able to implement the matchmaking perfectly fine inside of Blueprints but I wanted to do it within UE4++.

Am I in the right file? Or should I be looking elsewhere, besides the ShooterGameSession file?