[header] How to activate 2 step verification in facebook [title] Install the facebook app on on your mobile phone. [step] Facebook uses a code generator tool in the facebook app as a two-factor security system. You'll be prompted to open the facebook app and enter the code from the code generator. 
This only happens when you log into facebook on an unknown computer. If you can't use the facebook app or code generator, facebook will send your phone a text message with the code.