1.First, select the layer that you would like to crop in the layers palette. If the layers palette is not visible, go to Window > Layers.
2. Select the part of the layer that you wish to keep. To do this, draw a marquee around this area with the selection tool. (A marquee is the rectangle of dashes that delineates a selected area). Here, a marquee is drawn around the elephant so the extraneous field in the background can be cropped away.
3. The Photoshop function Select Inverse allows the user to select everything outside of the original selection. While a portion of the layer is selected, go to Select > Inverse and right click the selected and click Select > Inverse. The keyboard shortcut for this is Shift+Command+I. The new selection will be indicated by a marquee around the border of canvas and another around the original selection. The selected area is now the unwanted field: the area between the border of the canvas and the edge of the original selection.
4. Now that the unwanted field is selected, it can be easily deleted: press the Delete button on the keyboard. The only part of the layer that remains is the original selection. De-select everything by clicking outside the selection or by pressing Command+D. The elephant can now be easily be moved or adjusted