spring install question

when installing springs, after you remove the shock assembly from the car, how do you remove the top nut on the assembly to seperate the spring and the strut? I was told I need an impact wrench. Or do I just need to compress and then I will be able to remove the nut.

An impact gun would be the easiest way, but there should be a hole at the very top for an allen wrench. So compress the spring so it can turn in the perch and just make sure you use a metric allen wrench or else it'll end up stripping the hell out of it. Then just use a wrench to loosen the nut while holding onto the allen wrench.