Add credit cards on the Settings > Billing Information page.
The first card added is marked as the "default" card and will be used for recurring billing such as payments for the Pay As You Go plan.
If you add multiple cards then you (and other admins) will be able to select which card to use during the checkout process for tools like premium job board posts and Workable Campaigns.
Click Edit to change card details, choose a new default card or remove a card. It is not possible to remove the default card without setting a new default. Select a different card to become the default before removing the original card.