Follow these steps to import voucher codes:
On the main menu, click Marketing.
On the Marketing Dashboard menu, click Offers > Discounts.
Start creating a discount like you do regularly.
On the General tab, under Vouchers, select Vouchers with consecutive numbers.
5. To import voucher codes, add the codes to a .CSV file and name the sheet
DiscountVouchers for successful importing them into the system.
Note: At once, you can import up to 20,000 vouchers. If you must import more,
you need to import them multiple times in chunks of 20,000 or less.
6. Complete creating the discount.
After you create the discount, you need to associate it with a Media campaign to send these codes to your target customers.