There is a special instrument in the row of Photoshop instruments on the left side of the screen, or you can markquee the field you need and then go "Image" > "Crop" on the top bar
An Special icon of cropping is given in the tool bar of photo shop use it and select the area which you really wanna crop form the picture..and after selecting crop area left click and select done...
Croping Image is very easy....just open Photoshop ...there is a tool called
Crop-Tool(C) on the left hand side....just use this to have any type of croping.