Couple things:
Is it a big section/pause that is hissing? If it's a big section, I will just highlight the area, insert silence and it will make the hiss go away. If it's a hiss that is going on when I'm talking, you ccould try to highlight the section and reduce the volume to help it.
I've never really had good luck getting rid of the hiss if it's happening when I'm talking. I usually end up rerecording the audio. BUT when you record make sure either your computer master volume and/or your microphone volume is lowered . I realized that mine was really high, and once I lowered it the hiss MOSTLY went away.
Hope that helps!
