To deploy a bot on Whatsapp using Twilio, you will first have to setup Twilio Messaging Services by following the instructions in this article.
Once Messaging services are setup, you will have to request access to a Whatsapp business account.
You can do so directly from the Twilio dashboard by going to Twilio > Messaging Services > Senders > Whatsapp senders.
You will be redirected to a form where you can request access to the Whatsapp senders.
Submit a request to activate your number.