Q: How does a new apple user figure out how to save files to subfolders?

Once you get to the Save As window, select Documents.  When you get the Documents window, select the sub folder that you want.

http://support.apple.com/kb/HT2477 

New to Macs/My First Mac

After opening the Save or Save As window, you may need to push the button with the triangle before the subfolders will appear.

(107740)

An extension to what Niel said.....

Click on the triangle next to the Save As window.   Make sure Documents is shown in the Where: window.

Your next window will bring up the Documents window.  Highlight the folder you want and double click same.  This will bring up the sub folders.