1. Just put in extensions folder twilio folder
2. Copy extension/twilio/settings.ini.default.php to extension/twilio/settings.ini.php
3. Execute

php cron.php -s site_admin -e twilio -c cron/update_structure

or https://github.com/LiveHelperChat/twilio/blob/master/doc/install.sql

4. Enable extension in settings/settings.ini.php

'extensions' =>
      array (
        'twilio'
      ),

5. Clear cache from back office.
6. Twilio module you will find in left menu under Modules.
7. Register phone from Live Helper Chat back office.

Settings should look similar to this. P.s I have changed phone number and Account SID with Auth Token

If you are using WhatsApp phone number should look like whatsapp:+14155234444

6. Send SMS to registered phone number
7. Enjoy :)

Callback URL you will find once your register phone in back office.