If you have credits from referring friends to online kids consignment shop ThredUP, today’s the day to use them, because you can get your order shipped free with coupon code FREESHIP.
If you have the $10 signup credit, I don’t think you can use that and free shipping at the same time, because both are coupon codes. But credits on your account from referring other people should work fine.
Disclosure: Affiliate link above. You buy, I earn credits.