how can i get my freezer to stop over freezing candys fridge freezer?

since i have lost the manual i cant look to see what temp it is ment to be on at the moment it is on 3 1/2 but the freezer door is opening up with all the ice i have tryed to defrost it and it was good for about 3 days then it was back to square one again i would appercate all the help i can get thanks