Select what you want to transform.
Choose Edit > Transform and choose one of the following commands from the submenu:
Rotate 180° to rotate by a half‑turn
Rotate 90° CW to rotate clockwise by a quarter‑turn
Rotate 90° CCW to rotate counterclockwise by a quarter‑turn
Flip Horizontal to flip horizontally, along the vertical axis
Flip Vertical to flip vertically, along the horizontal axis