Ok let me start off my saying this isn't the most detailed guide you'll ever read, but the major steps are here...any questions...just ask!! :P
This is the kit I installed which I purchased from here:-
Undo the flat head screw on the jubilee clip and wiggle the rubber pipe free from the stock air intake plastic housing
At this point just wiggle the whole intake housing free, no for
may need a little help from a flathead to be removed but again no force
needed at all.
I then removed the two rubber holders shown below as I did not wantthem to fall out later and I stored them away with the stock intasksystem.
Also, feel free to check out my complete build thread for my Fiesta ST-2:-