Changing a car strut?????????

Hello, Im changing a front car strut. The spring broke so it was easy to get off. I do have the spring compression tool, and I compressed the new one and assembled the strut/strut mount/ and spring. However the top but that holds the strut mount to the strut will only tighten a little and then the whole strut spins around with it (the center) How do I get this not to happen so I can tighten it and but it back in??? There is no pressure on it I had the spring compressed. Thanks.|||we use an air gun at the shop|||Put vice grips on the shaft towards the top of the shaft which you will need to release the compression tool to get between the spring coils.