How to update already existing data via import.

How to update already existing data via import.

HI all

Kindly help with below 

I have a set of data in creator app. for example 

Name | Email | expiry date.


The expiry date changes based sales activity offline, which is reported as CSV with  Email and expiry dates.

how do i import the offline sales activity report so that it updates the expiry dates for the email address already available in APP.