While sometimes a screaming problem starts because of boredom, loneliness, or frustrated mating desires, it is very common that screaming develops because an owner has inadvertently reinforced the behavior by rewarding screaming with attention. The problem doesn't develop overnight and there are no magic cures but good discipline and careful alteration of the owner's behavior patterns can often solve it over time. If the bird is boss in your house you will probably have behavior problems at some point. See the FAQ on training and taming if you aren't familiar with these. Next, you need to establish a routine for your bird care and for your interaction with the bird.
Birds are creatures of habit and they like their lives predictable.
Excessive spontaneity makes them nervous and insecure and when they are feeling this way they are more demanding of their human companions. Scheduling several shorter times during the day when you will be with the bird is better than having one long time that lasts for several hours but not having any other playtimes. Next, you will need to consciously alter your own behavior. Sometimes, people have had good results with quietly and quickly dropping an opaque cover over the cage when the screaming starts. If you try this it should be done with a minimum of fuss and the cover should be removed again as soon as the bird is quiet.