pre how do I put a card on the prepaid pre-authorized credit card

You should be able to set up automatic 30-day top-ups on your Self-Serve account. If it does not work, you can also dial *611 and follow the instructions when prompted to make the payment over the phone. https://www.koodomobile.com/en/help/topping-your-prepaid-account

Are you referring to a prepaid account or a prepaid credit card?

If you want to add your credit card for auto top-up on your prepaid.

From Koodo Chat:

Log into self serve.

From the Overview page, click on the "Billing" tab.

Select "Sign up for Automatic top-ups" to register a credit card (Note: If you are already registered on Automatic Top-ups, this section will be named "Manage Automatic Top-ups").

Fill in the following mandatory fields or update your info as needed(Note: Address must match the address registered with the financial institution to avoid an error).

Click "Save".