Go to Menu (on top left)
Click on profile from the left pane you will see a button provided for verify of Facebook and phone number.
Click on verify phone number button and choose manual Instruction.
You will be provided with a 4 digits code and foreign phone number.
Send the 4 digits code through SMS to the foreign phone number.
After the SMS is delivered, Click on I HAVE SENT THE TEXT button
A message will show up that you have verified your phone number
Click on Verify button
Follow the prompt page and click allow to verify your Facebook