It's not automatic!
On this page: https://tapas.io/Xzynder you can see your subscriber number over on the left. Click that, and you'll be taken to a list of your subscribers -- click on any of them to go to their profile. And if you're logged in, then on your profile you should be able to see a space in the middle, with your icon, that says "share something" right above their wall. You can start typing in that space, and click share, and it'll post to their wall!