Install/update the latest version of WhatsApp on your phone.
Ensure that you have an account with one of the banks that supports WhatsApp Pay.
Your WhatsApp number should match the phone number associated with your bank account.
Open the latest version of WhatsApp on your device. Choose "Payments" from the menu that appears when you tap on the three vertical dots that appear in the top right corner of the screen.
Tap the "Add Payment Method" button on the screen. From the list that appears, select the Bank where you have an account and want to link for payments.
Click "Done" one last time to complete the payment setup. On the Payments page, you can now view your UPI ID, payment history, and connected bank account information.
On WhatsApp, open the chat screen of the contact to which you want to send money.
Tap the attachment button (paperclip icon) that you can see in the message box and select the “Payment” option.
The Send Payment page will appear. Enter the amount of money you want to send to your contact. Add a note for the amount if you wish. Tap "Next" and then the "Send Payment" option.
Finally, enter your UPI pin to complete your transaction.