Hi Hari,
Below is the process flow to test payment order given the fact that all the necessary configurations are already done.
1. Create a receivable and assign payment method, bank details and paying company code i the dcument as that of the payment order.
2. Run FPY1 for the document
3. Check in FPL9 that the debit receivable has been assigned with a truck sign meaning that a payment order has been created to clear off this debt and this debt will not fall under any recovery process.
4. Run payment medium (program SAPFKPY3) to check correct information is populated in the bank notification file.
5. Once you receive clearing information from bank, create payment order lot using FP45.
6. Once the lot is posted, the debt will be cleared and the clearing document will be a payment document.
Hope it helps.
Let me know how you go.
Thanks
Bodhisattwa