For multiplayer you need to get your route completed as best as you can.
Now in the session go to session add the multiplayer rule.close the session,save.
Now right click on route go down to upload.Upload route to the DLS.
Do the same with the session.Now in about 3 days it will be on the DLS for you and others to DL and use to multiplay.
Just remember that ALL assets MUST be BUILD-IN or on the DLS or it won't work.(no 3rd party assets)