Hi Fotograf R,
To solve your problem please go through the following link
Best of luck
Join me on Google+
Hello and welcome,
In order to use the coupon, go to Billing Tab and then under More actions select apply a promotional code. Here you need to enter the code. Find more details here: https://support.google.com/adwords/answer/1703648?hl=en
Make sure that your account fulfills all the terms and conditions before you redeem the code.
Hope that helps!
Re: Cupon code
Hello Fotograf R,
Welcome to adwords community,
Promotional codes are usually only meant for new advertisers, providing an easy way to get started with the AdWords program. Therefore, these codes can only be redeemed up to 14 days after the creation of an AdWords account. If you created your AdWords account more than 14 days ago, you won't be able to redeem the code.
promotional codes require you to meet certain criteria in order to get the monetary credit. For example, if you're redeeming a "Spend $25, get $50" offer, you'll have to apply the promo code and then get at least $25 worth of clicks in your account. After spending $25, you'll then see the $50 credit appear in your account within 5 business days.
Hope it helps you