1992 Buick Century need to pull and replace the crankshaft

I'm assuming you already have the engine out of the vehicle.

You need to purchase/rent a "Balancer" puller. It looks like three metal arms with a single bolt running through the middle. It comes with adaptors to fit different sizes.

If you ask a parts store clerk, they'll know what you want and give you a quick explaination on how to use it.