Hello Prasanth,
There are some modules in the marketplace that can maybe help you with that:
https://marketplace.mendix.com/link/component/208935
Otherwise, you can make use of the api of whatsapp:meta:
https://developers.facebook.com/docs/whatsapp/cloud-api/reference?locale=en_US
hope this helps,
Good luck!
Do you want back-end integration with WhatsApp for Business? (Then Jelle's answer provides a start)
Or do you want to present a link to chat easily with some number?
The latter can be easily implemented by adding such a link:
https://wa.me/1234?text=I'm%20interested%20in%20your%20car%20for%20sale
See for more documentation: