Please please stop your son banging on the cage... for your son's sake. The bite of a ringneck can be extremely painful. Not to mention this is incredibly stressful for the bird. I would advise putting the bird is a quiet room and perhaps not allow your son in the room. After a week or so go into this room and sit with your new bird talk to him just sit with him reading a book or perhaps watching a film or play him some music.
Gradually you can start with the taming which you will find in Michael's guide on this forum. Very useful

Additionally, please ensure you bird proof your home:
No air freshners
No strong fumes
No Teflon Pans (buy stainless steel or glass cookware)
No perfumes
No candles (scented or otherwise)
No loose fittings (blinds should have the strings tucked away to prevent accidents)
No metal things that can be chewed (this will cause heavy metal poisoning) Stainless steel is fine
Use only bird safe disinfectants- f10, bird safe johnsons are two good brands.
Right now you need to create a quiet and calming environment for the bird. Your bird may never talk and this should never be a reason for buying a bird because of the novelty of talking. The noise will come but it may never ever talk. Also you need to go to an AVIAN vet for a new bird check once he's settled. You will need to train him into the travel cage which will take some time. This will be easier once you've mastered the taking treat from the hand scenario.
If you're not willing to put in the work with this bird and just want something that can talk then please allow someone with more experience to take care of the bird. I'm really not a fan of pet shops, they know very little about the animals they care for in my experience. Birds are very different from other animals.
Diet wise you will need to have pellets, seeds and fresh fruits and vegetables. Although please check before you give each food to check its not toxic. All birds are lactose intolerant also. You will also need a good selection of natural wood perches to help the feet and nails. Pellet conversion is difficult and if not done correctly you can end up starving your bird so read u[p on the various threads on this forum
make sure you clean and sterilizee bowls each day and fresh foods should not be left in the cage for longer than 2-3 hours. The dribnking water should ideally be filtered or mineral water. Tap water can contain some harmful bacteria.
Leave the bird alone for at least two weeks, it won't harm him providing he is in an adequate sized cage. Cleaning the cage can wait but if you have a remoavble grate and bottom maybe do this after a week or so as you don't want baceria building up.
Please please treat this bird with respect and compasson not a performing circus animal.