You can learn what access tags are here

First go to "My magazines" and "Members"

On the page that has opened you can see all your members. Click on "Action" and then "Edit"

In the dialog that opened you can now add/remove access tags under "Access tags"
The user can now read any magazine that has the correct access tag in a valid Kiosk. 

Make sure that the magazine is blurred out, otherwise anyone can view the magazine. Learn how to do that here