For producing different pitches on your sitar, you may put your left index finger on the string at the aimed fret while plucking the string by mizrab.
Finger position is not on the fret itself but just side way of the fret. If your finger is on the fret, then the sound won't be clear but dumped.
Carefully look at the proper position in the Movie 04-1: "Left index finger position, side view," and Movie04-2: "Left index finger position, front view."
Movie 04-1: "Left index finger position, side view"
Movie04-2: "Left index finger position, front view"
