After a successful transaction, here is the flow of actions:
1. Merchant gets a notification on the mobile on his/her UPI app (Google Pay/PhonePe/BHIM…)
2. Merchant opens notification, sees a payment made. Sees the “Order ID”
3. Merchant opens the Woocommerce Dashboard, checks the “pending orders” for this Order ID
4. Checks the order details and processes it (shipping etc) and makes the orders as “completed”
So, after successful transaction, you have to approve it and complete processing of order in Woocommerce as you would be normally doing