put the car in 5th.
also remember to replace the bolt when you put everything back together. I imagine you are doing an underdrive pulley swap.
use the stock bolt to torque the pulley on initially. Once it is threaded, tighten it to 240 ft. lbs. or until it is completely seated on the crank snout. Afterwards, remove the stock bolt and replace it with the new crank bolt. You will tighten the new bolt to 37 ft. lbs. and then turn it an additonal 220 degrees