Just getting started and maybe a dumb question

I've used Final Cut for years but only now have decided to try and learn SoundtrackPro. I'm using the book "Sound editing in Final Cut Studio" by Jeff Sobel, and already by page 21 I'm stumped. It's his lesson on "Separating Signal from Noise". An audio clip to use in this lesson is included in a DVD that comes with the book. One selects the clip in Final Cut then sends it to Soundtrack Pro. Fair enough. But once in Soundtrack the instructions simply say "select a portion of the audio where the waveform appears basically flat". But how? Nothing more is said, instead we just see a picture of a nice little section of the otherwise green waveform shaded blue after the playhead. No markers. No In and Out points. Nothing else.

I've scoured the on-line manual looking for help in figuring out the recipe for "selecting a portion of the audio". Under "Set Noise Print" I've found basically the same words as Mr. Sobel's - I'm just told to "select a portion of the audio".

Well, as I say, I've hit my wall at page 21. Can anyone out there tell me how one "selects a portion of the audio" in the Timeline? (And Mr. Sobel does this with establishing In and Out points like you'd do in Final Cut.) With someone's help out there maybe I can get to page 22.

Thanks.

John