To set mail for Request payout/Affiliate Application/Credit Added/Affiliate Applied,
First, you will need to go to Email in the WC Affiliate setting.
After that, You need to enable the mail option which mail you want to give your affiliate.
For Affiliate applications, enable mail for Affiliate applications.
For Request payout-
For Credit added-
All you need to the same process for the Confirmation mail. Finally, click on the Save button.