First you must have visited the 'My Stone Family Rewards' section of your account on https://www.volcom.eu/ and input your birthday month and day at least 30 days before your birthday. 

To prevent abuse of this reward, if you input your birthdate a day after your birthday, you won't be granted your Birthday Reward until your birthday the following year. If you entered your birthdate less than 30 days prior to your birthday, your Reward will be granted in delay, up to 30 days. If you entered your birthdate any time prior to 30 days of your birthday, your Reward should have been granted normally on your birthday. 

The Reward will be sent to you the exact date of your birth!