Redeem an ad credit with an ad credit code
1. In the Payment Method section, click Add Payment Method.
2. Select Facebook Ad Credit.
3. Enter your ad credit code and then click Apply.
4. Click Continue.
5. Create a new ad in Ad Center or Ads Manager.
Redeem A Facebook Ad Credit With an Ad Credit Code www.facebook.com > business > help
Nowadays, however, the new improved Facebook makes gift cards available through Target, Safeway and other online ecommerce sites, but oddly doesn't allow you to buy Facebook credits as a gift on the site itself.
Can I still gift someone Facebook credits? - Ask Dave Taylor
www.askdavetaylor.com > can_i_still_gift_someone_facebook_credits
If you are a occasional or regular advertiser on Facebook then you need to go to Payment Method Section in the Ad Manager located under the Billing Section. Click the New Payment Option where you can select Facebook Ad Coupon. Here you can enter the coupon code and continue.
Want To Get A Free Facebook Ad Coupon? - Digital Vidya
www.digitalvidya.com > blog > want-to-get-a-free-facebook-ad-coupon