To redeem a coupon code log in and go to the 'Credits' tab in your online Bark Account. Scroll down to the section labelled 'Redeem Coupons'
From here, just enter your coupon code and click 'Redeem'.
This will bring up your discounted credit pack options. Select the pack that you desire and click 'Buy Now'.
Your new balance will then be updated in the credit section.