I don't have a Mac so IDK.
But you need to have a session that someone is running.
It needs to be on the DLS or Built in.
If you DL a route & session that is for MP you can start it your self.
,and mabe someone will join you?
Don't know how big of a route a Mac can handle, you may DL Thompson and Western session 1 <kuid2:105915:100081:1>Arthor danny5 (created by GN1996)
After DLing it,right click on the session go down to view dependences,then view in main list,scroll down if you see any puzzes right click on them and DL them.
Everything in this route/session is built-in or on the DLS.(content manager)