help! cant get the decreasing tip

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please i cant understand how to do it!
DECREASING TIP: Make all dec from RS. Dec 1 st on each side of st with marker as follows: Slip st before st with marker on cable needle behind piece, slip 1 st as if to K, (= st with marker), K tog next st and st on cable needle, psso (= st with marker).
can someone write the same but more simple??? how i should use that cable needle??? do i need two needles?? normal and cable? cant get it at all........ help help!!!