Configuring RFC from PI to update a field in KNA1

Hi All,

We have a requirement to update a field in SAP ECC system using an RFC call from SAP PI.

The data flow is to be Legacy System -> SAP PI -> RFC Call -> Field in KNA1.

Kindly help me understand -

1.Configurations to be done in SAP PI 7.4

2.Configurations to be done in ECC.

Please share any documents/links which can be helpful in setting up the above flow.

Thanks,

Ravi