To set up for the spider curl you need to either use a preacher curl bench in the opposite way or an incline bench at about 45 degrees laying face down.
Grab dumbbells or a barbell and hold it with an underhand grip around shoulder width apart.
Position yourself with your stomach on the padding and arms hanging off the high side.
Keep your eyes facing forward and slowly curl the weight up as far as possible.
Squeeze the biceps, pause, and then slowly lower the weight back to the bottom.
