How send PM to fb messenger from FB fanpage.

Hello guys
I want ask about one think. I have one page (fanpage) on facebook.
I want ask how I can send PM to my page followers ?
I ask because I of course follow some pages on facebook too. and sometimes this pages send me PM. to my fb messenger. And it's not only one time, few times per month.
But how do they do this ? I don't have any idea.
Maybe you can tell me ?
Thanks

You can't initiate contact with a personal profile from a business page. The person has to initiate contact with your page first (message your page, comment on a post, etc).

OK I understand, I sent 1st some message and got auto respond, but later non stop they send me messeges 1-2 per week.
But how it work that automaticly they send to all user which sent them some message before, lot messages. I think famous person which has 9.000.000 fans , not send to everybody personal message. There must be some auto system to send to all user which in past send them some message.