There is a screenshot button resent in hyperon or jellyblast roms . But it is very much easier to take screenshots of your mobile without any root or any app . 3 simple steps and your work would be done .
Steps to take screenshots on galaxy Y :
1. Go to any app you would like to take screenshot .
2. Press and hold your home button and immediately press power/lock button . (If it opens task manager you didn't do it correctly .try again )
3. It will play a shutter sound and screenshot is taken . It would be saved in screencapture folder. You can go to gallery and find it there . .
Thats it . You have captured screen perfectly .