When creating a payment link for a specific customer, the "Reminders" option can be set. You can also specify the date when the first reminder must be sent.
If your "Send e-mail" option is not enabled at the payment link, the reminder will only be visible in the RCUR dashboard on the "Reminders" page.
If you have also enabled the option "Send e-mail", a first e-mail will be automatically sent to the customer on the reminder date. After this we will send a reminder every 3 days. The email text can be adjusted in the settings of RCUR.