As soon as you start a stream, i.e. go live, it is visible to everyone - as long as they join the stream, of course. If someone calls up your profile, the banner "is currently live" appears there.

Let your fans know when you are going live by sending them a message with the time and topic of the stream.

Open your profile > Your fans > "Send your fans a message". And pack the good news into a crisp 250 characters.