1) When you click below link:
https://eservices.cic.gc.ca/epay/
You will get in landing page
2)press "continue" and u will be taken to another page; then click immigration
3) click on payment service type i.e. right for permanent resident fee
4) enter quantity and hit "next"
5) then login with your eservice credentials and make the payment.
Once the receipt(receipt number starting with RXXXXXXXXX) is generated you would need to upload it in the cic account, under "view submitted application" section.
Note: It is recommended to pay RPRF only when asked for cic through message.
Refer below link for details:
www.cic.gc.ca/english/information/fees/index.asp