Put the new bushing on the bolt, insert it through the spring, place the other bushing on and tighten the nut until the same number of threads are showing above the nut as it was before you re- moved it. Then you can lower the jack and move over to the opposite side of the car.
Here’s what it looks like with one side of the spring done; now repeat all of these procedures for the opposite side of the spring and you’re done.