Lowering Springs Help...

Hi, this may sound stupid and noobie but i've bought a set of 1.5" lowering springs and i was wondering if anyone has done a D.I.Y on this? because i can't find a decent one anywhere else and to get them fitted by a garage it will cost £150 +, i do know what equipment i need, its just how to install them i'd like to know. cheers 
