To unblock an app:
Navigate to your Privacy Preferences Page
Click Manage Blocking across from Blocked People and Apps
In the Blocked Apps section, find the app you want and click Unblock
You'll need to grant the app permissions again if you would like to re-add it to your profile (timeline)
To remove a block you've set on someone:
Click the account menu at the top right of any Facebook page
Select Privacy Settings
Under the Blocked People and Apps section, Click "Manage Blocking"
Click "Unblock" next to the person’s name
Please note that this will not automatically add the person back to your friends list. If you want to become friends with this person again, you'll need to send him or her a new friend request.
There is an in-line audience selector on the app install screen that controls who can see your activity from that app. After you install an app, you can view and manage its settings on your App Settings.
To get to your App Settings:
Open the account dropdown menu at the top right corner of Facebook and click Account Settings.
From the menu in the left column, select Apps. From here, you can manage settings for each individual app you've added.
To change who can see your app activities:
From the App Settings page, click Edit next to the app you’d like to change
Across from App activity privacy, choose the group of people you’d like to share with using the dropdown menu
To get to your general settings for Apps and Websites:
Click at the top-right corner of Facebook and pick Privacy Settings.
Under the Apps and Websites heading, click Edit your settings. From here, you can turn off all platform apps, control what information is visible to your friends through apps and websites they use, and more.
Last edited: Apr 27, 2012