How to join groups in Forza Horizon 3

So I was curious to this so I know people can start a group, but how do I join someones group. I am not talking about clubs. For example Johniwanna hosts a twitch/Beam stream every friday and invites players to join him. My question is how would I join him, and if I was streaming how could I do the same?

If they are on your friends list they should show up in game on your map as blue circle, join off that.

Or

In start menu in game they should appear on a tile towards the right.

Or

Go to their gamertag and full profile and join game from there.