Instructions:2-4-1 on coke zone. You need 5 points to get it, which you can get on sign-up.
To get this, simply sign up to CokeZone. You will be given a 2 point start up bonus. On the second page of the sign-up, you will be asked to take part in their survey (which you need to fill out anyway to receive your rewards from CokeZone). This will grant you a futher 5 points.
You get a link to these locations to get your vouchers: