The first thing you have to do is determine why the bird is screaming. Is it boredom, is it lonely, is something bothering it or scaring it, or is it sick?
Quaker parrots are very much a flock bird and wild Quakers spend hours building elaborate nests that are huge. This is what comes natural to the bird. If it is stuck in a cage alone without a human flock spending time with it and doesn't have shreddible toys etc. then it may be screaming because it is unhappy.
We do have training articles on our Parrot Training page that may help you to spend time with your bird teaching it a replacement behavior for screaming.
If your bird hasn't been examined by an avian vet, then I also suggest that you Find an Avian Vet to examine your bird to make sure it is healthy.