Firstly make sure you dont cut it too short (Done it before
)
Use cable clippers/Wire clippers to chop it off
Then your going to need trim it so the cable inside the cover is showing a few CM's
^ All that can be understood by simply looking at the end of the cables in the current state.
Attach the little ends on that hold it to the screw in point on the box and your done.
(This is for both cables as you have stated SKY+)