Perspective gives your image a three-dimensional appearance by applying a warp along one or more planes. By reshaping a supporting perspective grid you can transform your image.
To apply perspective:
From the Tools Panel on the left, click the Mesh Warp flyout, then the Perspective Tool.
(Optional) For two opposing, but independent, perspective planes, select 'Dual Plane' on the Planes pop-up menu.
(Optional) Use the Mode option to set the mode in which the grid will operate. 'Destination' shows the image with perspective applied. 'Source' lets you size, position and shape the grid without affecting the image; you can then apply perspective to the image by jumping back to the 'Destination' option and dragging handles.