How to install the coil on plug?

That doesn't make sense. What are you trying to do? replace a coil pack or plugs. And on what size motor?
 
That doesn't make sense. What are you trying to do? replace a coil pack or plugs. And on what size motor?

I've installed them successfully today. Turned out I didn't have to do any length adjustment on the coils.
I was trying to change the boots right under the 2 coils packs on cylinder 2 and 4. The buttom part of the rubber boots of old ones broken off when I took them out for a spark plugs change.
 
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