To get $20 off any purchase - open Pinterest app on any Android device and make sure it's upgraded to the latest version.
Shop anywhere on Pinterest and look for Pins with a blue price.
Click on the blue "buy it" button and check out with your MasterCard.
You have to use an Android device and MasterCard. Purchase must be made directly on Pinterest through "buy it" button.
Found on Pinterest: https://help.pinterest.