The Transform submenu of the Layer menu contains commands which flip or rotate the selected layers of the image.
You can access this submenu from the main menu through Layer → Transform.
The Transform submenu contains the following commands:
Section 7.46, “Flip Horizontally”
Section 7.47, “Flip Vertically”
Section 7.48, “Rotate 90° clockwise”
Section 7.49, “Rotate 90° counter-clockwise”
Section 7.50, “Rotate 180°”
Section 7.51, “Arbitrary Rotation”
Section 7.52, “Offset”
