After successfully installing the Mobile Number Verification addon you need to configure it. For SMS Gateway, we have Google Firebase and Twilio options.
To use Twilio. Create an account on www.twilio.com site and explore available SMS package. Add following settings after create account from WordPress Dashboard => Classified Listing => Settings MISC
Twilio SID: Add Twilio account site ID here.
Twilio Auth Token: Add Twilio account authentication token.
Twilio Phone: Add Twilio account phone number.
OTP Resend Time: Add OTP resend time in second in seconds. It also will be use as expire time.