Go to the dashboard
Wordfence->Advanced blocking
and follow the instructions there.
if they are all in one range you might be blocking something like
69.175.0.0 - 69.175.127.255
Make sure you really want to block the range you input. In the example above I am blocking 32,768 IPs all located at a server farm in Chicago. I don't need server visitors (mainly bots), I want people.
