yes, thats all you do, except you also shorten the strut body to suit the insert and the stroke point/range you want the dampener at at your approximate ride height.

so for a normal ae86 coilover, you really only have a range of say 2" of height adjustment. this should be plenty for most people. stuff like greddy/HSD are base height adjustable, like most coilovers for other imports, so theyre different.

a spring is basically a peice of wire you are twisting. usually we talk about them being rated in KG/mm. you cant make them stiffer by preloading them, nor should you. each extra xKG compresses them an extra xmm.