Hello i need help on creating a button. I want to create a button in Payment file administration record. how to create? is it on transaction body field? or something?

If you're creating a button, I think you'd need to do a workflow. Or do you mean a radio button? Either way, yeah it would be against the Payment File Admin record. For the radio button, you'd need to go to the PFA custom record and add the field from there. Adding custom fields to custom records must be done from the custom record.