Follow the steps below to add Cashfree Payment Gateway in your Magento Store. ( Go to the documentation for details)
Step 1: Log in to your Magento Dashboard. Click Configuration from your Store page inside Magento Dashboard.
Step 2: Choose Payment Methods from the Sales dropdown menu on the Configuration page.
Step 3: Enter your Cashfree Merchant App Id and Merchant Secret Key Available on your Merchant Dashboard
Learn the integration in detail here in the documentation.