Call the Free Transform and Transform commands in the Edit menu to apply transformations to the selected layer or object. The transformation parameters are displayed on the Settings Panel.
Note: If you want to transform the entire image, you should select the needed operation in the menu Image -> Transform Image. In this case, all layers of the active image will be transformed.
To transform the contour of the selection, use the Transform Selection command in the Select menu.
Transformation Options:
Shift. You can change the position of an object horizontally (X) and vertically (Y). The parameter uses the coordinates (in pixels) of the upper left point of the bounding box or of the center point (if the sign 
is activated). Usually the center point is fixed, but you can move it to the different location.
Place the cursor 
inside the bounding frame and drag the object. If you bring the cursor to the center point, you will get a pointer with a circle 
- now you can move only the center point.
Before Moving Object
After Moving Object
Scale. You can adjust the size of an object in width (W) and height (H) (in percent). Drag one of the eight square markers on the frame to increase or reduce the size. The cursor will turn into a two-sided arrow 
. Use Shift-key or press the sign 
between W and H to constrain the proportions of the object. If the sign is deactivated 
the proportions can change. Hold down the Alt key to scale a fragment or a layer relative to its center point (transformation center).
Original Size
Scale Increased
Skew. You can shift some parts of an object relative to the others. When you bring the cursor to the frame, it will look like this 
. Press and drag to transform the object. Hold down the Alt key to skew a fragment or a layer relative to its center point (transformation center).
Source Object
Object is skewed
Perspective. You can alter the perspective of the selected object and fix perspective distortions. Select Edit -> Free Transform... and move the corner markers while holding down the Ctrl key. Each marker can be moved independently of the others, which allows you to easily change the perspective of the selected object.
Original Perspective
Modified Perspective
Rotate. You can rotate an object. The center of rotation can be changed by moving the center point of the object. Outside the bounding frame the cursor turns to a rounded two-sided arrow 
. Holding down the left mouse button, rotate the object clockwise or counter-clockwise. If you press Alt, the rotation angle will change in five degrees.
Before Rotation
After Rotation
Click the Reset Perspective button to reset the changes you made to the perspective. The transformation will be determined by the parameters in the settings panel.
Click the Reset Center button to restore the center point in its default position.
Press OK to apply changes. To cancel the transformation press Cancel or use the Esc-key.
Also, you can apply transformations using the following commands from the Transform submenu:
The commands Rotate 90o CW, Rotate 90o CCW, and Rotate 180o rotate the image to specify degrees.
Flip Horizontal. The command allows an object to be mirrored along the standing axis, i.e. interchanging the left and right sides.
Flip Vertical. The command mirrors an object by turning it upside down.
Before Transformation
Rotate 90 CW
Flip Horizontal
Flip Vertical