It's at https://www.facebook.com/. If you're already logged into Facebook, doing so will open your News Feed.

If you aren't logged into Facebook, you'll first enter your email address (or phone number) and password in the upper-right side of the page.
 It's in the top-right side of the Facebook window., This option is near the bottom of the drop-down menu., It's a tab on the left side of the page., You'll see the name of each person you've blocked in the "Block users" section of this page., Doing so will unblock your selected user.

If you want to re-block the user, you'll have to wait for 48 hours before you can block them again.
Go to Facebook's website.
Click ▼.
Click Settings.
Click Blocking.
Click Unblock to the right of someone's name.
Click Confirm when prompted.
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