Click on the hamburger icon in the top left (looks like three vertical lines). That will trigger the menu to display. Then click on Manage > Basics. Then click on Top Left icon again to see all control panel areas, including Permissions and Circles.
It looks there is a bug in that the CP icon I referred to is really hard to see (due to the color assigned to it, but just click on that top left corner and you will see the menu). We will fix the icon color issue soon.
When you block a person, they can no longer invite you to a private message or post to your profile wall. Replies and comments they make will be collapsed/hidden by default. Finally, you'll never receive email notifications about content they create or likes they designate for your content.
Note: if you proceed, you will no longer be following .