Enter recovery mode:Press and hold Vol+ ,home, power key (Device open after release power key keep vol+ and home key).After you see droidman :D.
1-Copy CWM-SuperSU-v0.97.zip to sd card and rename to update.zip.
2-Insert memory card to device.
3-Enter recovery mode and select apply update from external storage ,install update.zip.
Ok ...Now you have rooted Galaxy and more fun.