You can wrap a belt around the HB and waterpump pulley so that it tightens on itself and hold it in place. Or find a way to hold the flexplate.

Remember that heat burns the rubber face, so if this balancer isn't bad and you're removing it for another reason, flame would be bad.

Remove the plastic cover beneath where the engine and trans bolt together. It's actually a 2-piece cover, three 10mm socket head bolts. One forward, two below IIRC. Then stick a socket extension through one hole in the flexplate so it jams up against the under side of the motor as you try to break the bolt free. Think about the direction it will turn when you do this.

You will likely need a cheater pipe or long breaker bar. If you have an impact wrench, you don't even need to hold the flexplate. Tightening is the reverse.

PLEASE NOTE:
If you borrowed or rented or purchased a puller (I hope you did, you need one), the bolts are NOT likely in the kit. You need three M6 bolts to thread into the balancer. If you use the wrong thread pitch, you WILL strip out the holes and cause a major headache.

There only 3 open slots in the HB and the bolt holes are directly in the center of those but recessed.

You have to use the correct bolts. If you need something to match it to, it's the same thread as the upper intake to lower intake bolts. I just use 3 of the longer ones usually near the throttle body since I have them laying around.

Remember that heat burns the rubber face, so if this balancer isn't bad and you're removing it for another reason, flame would be bad.

Simplest way....loosen lug nuts on the passenger wheel, jack up car on passenger side front,set jack stand, remove passenger wheel, remove splash shield on the inner fender wall, loosen serpentine belts off the balancer, use an electric impact tool to remove crank bolt, use Lisle puller 45300 to remove harmonic balancer (Sears sells it). Installation is the reversal of the above steps. I used my inpact driver to set the crank bolt back on. I'm a 2-2.5 on the mech scale and it took me less than an hour! Be sure you put the belts back on straight...it'll squeal if you don't....ask me how I know!

Most electric impacts don't stand a chance if the crank bolt is properly torqued. 95% of the bolts out there will require a HIGH quality pneumatic impact or a breaker bar with a cheater pipe.