Simply go to the "members" page, and enter your search info at the top, and click the "search" button.
There are two ways you can block a member. You can visit their profile, and hover / tap the little pencil icon next to their name and click "Block Member" from the drop down menu. Or you ca...
Simply visit your own profile page, and click the "more" link as shown below:
Go to your "Block Members" page in your settings. Find the list of blocked members, and click "Unblock" next to the appropriate member you wish to unblock.
Many ways: There will be no "add friend" link on them. Only a "remove from friends" link. You can also check your friends list on your profile or in the members page.