If you actually want to edit the original file then you should get a program like wavelab,soundforge or cool edit.
if its just cutting it then you click on the sample then press ctrl E deleat the unwanted bit and theres a disk picture you click on to save...but like i sed there are other programs that you should use for this sorta thing.
if its the attack/decay/sustain/release you wanna change then click the sample then click the ins tab and do that...if you wanna do somthing else then your gonna have to rephrase the question cos i diddent fully get you.

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