If your card costs coins and you don’t have enough coins in your account, you won’t be able to schedule your card to send out at a later date or time. You can purchase coins from your Add Guests/Recipients page after you create your recipient list. As you’re adding your guests You will see a running total of the coins needed to send your mailing. After you enter all of your recipients, you can click the gold “Buy Coins” button that appears at the bottom right of your list.
Once you have enough coins in your account to cover the cost of your mailing, you will be able to schedule it to send at a later date or time.
See also: How do I purchase Coins?