How can I obtain user opt-in for WhatsApp?

How can I obtain user opt-in for WhatsApp?

You may obtain the users' consent below: -During the online transaction process -While setting up user profiles and preferences -Via email, SMS, or within the mobile app -Via phone Interactive Voice Response (IVR)

For detailed opt-in requirements, please refer to WhatsApp Opt-in Guidelines.

You may also refer to the opt-in requirement in WhatsApp Overview and this guide on how to Apply Opt-in Flow to Chatbot.