Hello!
I think the most effective way to communicate with your team is email or chat in SFI.
You can send them group message at first to explain them how to start, how to make VP and so on.
But I think is best for them to comunicate in email, to know them better. And in chat if they have an important question and you two are online at the same time.
Stream is ok too, to remind them when to do their weekly Versapoints.
Have a wonderful day!