Trimming a recording

I understand that the scissors icon will help me trim a recording.  (1) I want to make sure I am not trimming out what I want to keep.  I THINK what remains behind (that is, is NOT trimmed out) is what is within the blue box of the timer, correct?  (2) I plan to trim on each end of the recording.  When I first tried to do this at the beginning of the recording, I expected the program to ask me whether I wanted to trim (remove) X to Y time, but I was confused by the program.  Can you please show me the link to specific instructions on trimming?  Thank you.