Where is username/library??

I'm so fed up with this. Trying to copy any recent mail and other recent personal data since getting this new iMac, I'm stonewalled once again right at the beginning. I am trying to follow some instructions for copying Mail preferences and it says: "q1uit Mail; open Finder window; navigate to username/library/preferences..." This is such a routine thing yet on this new iMac, in Mt. Lion, no such Library file shows up.

Can anyone tell me where it is and how come it is not simply where it always used to be?

I'm serious. This is nuts. I even restarted, then made sure to double click on the Macintosh HD icon on the desktop to be sure I was in the right place - I am never sure anymore since the sidebar is totally confusing as far as having other networked devices and external drives connected.

Anyway...where is it?

Or was this an incorrect instruction? Of course I see a Library when I access the HD; but once I then go to Users, no more Library folder.

Anyone?