You have to remove the coil/shock combo, disassemble it, hammer out the old studs and hammer in the new ones. Then reassemble. This is a good time to replace the shocks if needed.
And get good coil compressors too if you're going to DIY because cheap ones like the Harbor Freight ones I used bent and were scary. I think most shops would do it for you for probably $50-80 I'd guess.