It's very easy to use a code. Click on "Show coupon code". Copy the code and look out for the opportunity to use it.
Now that you have a code, let's use it:
1. Go to avis.com.
2. Click on "Reservation" and then on "Make a reservation".
3. On the new page, fill in the necessary information to personalize your car.
4. Click on "Discount codes", type the code into the field "Coupon code" and press "Search".