If you wish to provide personalized coupon codes to your affiliates then you can either use the regular import option and then manually select affiliate for each imported coupon or you can use the difficult API coding approach or you can simply import a list of coupon codes with the respective affiliates by specifying the affiliate's ID, referral ID or username.
To do so you'd prepare a list of coupon codes and affiliates and save these into a CSV file with content for example like:
Once you have the file ready you'd log in to your merchant panel and go to Banners->Banners manager where you'd edit your Coupons banner and under the Coupons tab you'd select the option Import coupons from CSV.
Once you click the button a new window will open where you'll need to select the fields/columns of the CSV file, upload the actual file, and run the import. The dialog on the screenshot is set to accept a file with the above-mentioned structure where the first column is the coupon code and the second column is the affiliate's username, referral ID, or internal system ID.