The unit-replacement strut has a detachable top section held by a clamp and two bolts.
When the damper inside a MacPherson strut wears out, you can buy a replacement cartridge which — depending on type — may or may not include new parts for the strut itself.
You will need a pair of coil-spring compressors. Hire them if necessary, do not use makeshift arrangements of clamps, wire or cord. They are unsafe.
Loosen the wheel nuts and raise the car on axle stands under chassis or frame members.
Remove the wheels, and open the bonnet or boot lid to gain access to the suspension from above and below.
Removing a standard strut