Your suppliers can convert a Purchase Order, that you sent them from the platform, into an Invoice and send it to you for payment on the platform. All such Invoices, that are converted from a Purchase Order, will be visible in Payments > Invoices Received section.
You can view the invoice details, approve or reject the invoice from this page. Once you approve the invoice, you will start seeing an option of Pay Now against that invoice. Clicking on Pay Now, you will be taken to the Make a Payment page where you have to choose the Payment Mode, apply discounts if any, and book the payment for approval and processing. Once the payment is approved by the required approvers, you can then process the payment using the appropriate payment mode.