If you're creating a new Facebook account and didn't get the code to confirm your mobile phone number: Make sure that you entered the correct mobile number. Don't use any special characters (+ or -) or leading zeros.
3. In the first field, which says ‘e-mail or phone number’, enter your e-mail address (which you used at the sign up process) or use your mobile phone which Facebook knows (you should have entered that before, when you would like to use this feature).
If you previously signed up with Facebook using a different phone number than the current one you have the mobile app installed on, just enter your email address and change your number once you are logged in.