[WIP & RFC] Document navigation to a new sect2

TBH, I am not confident on English and I do not document it well.
Please please please give me some comments, or modify it directly. :P

TODO LIST:
 - [X] Correcting, 1st round by @csware 
 - [X] Correcting, 2nd round by @ch3cooli 
 - [x] Testing chm file