This is a two-piece set and it includes:
One long pant
With arms at sides, place tape measure under your arms and run it around the fullest part of the bustline and across the shoulder blades.
Find the natural crease of your waist by bending to one side. Run tape measure around your natural waistline, keeping one finger between the tape and your body for a comfortable fit.
With feet together, run tape measure around the fullest part of your hips/seat, about 7 to 8 inches below your waistline.
For full-length pants, run tape measure along the inside of your leg, from just below the crotch to about 1 inch below the ankle.