Open your photo. Select Filter-Liquefaction, and choose the first tool that looks like a finger, that is, deform forward. Press the ""or ""key on the keyboard to adjust the finger size. Generally, if the waist is thin, the diameter of this circle is better to be larger, which is not much wider than the human body. When the center cross is just at the waist position, click the left button and drag the mouse to shrink inward until it fits.