Once you have successfully installed the extension, go to Stores -> Configuration to configure the extension for use. Here you can find a setting to enable or disable the extension.
Refund Request: Enable or disable extension from here.
Maximum Time Span Allowed to Request for Refund: Enter days to allow accepting refund requests from customers. After specified days, the refund request button will be hidden from their “My Account” section.
Email ID of Admin: Enter Email ID of admin to receive all the requests of customers into mail.
Email Template: Select template for refund request Email.
Email Sender: Select Email sender.