I opened the Vim user manual with the :h user-manual | only command (to open it in one window) and now I want to enter/open the separate text files. I tried to put my cursor over a section, such as |usr_01.txt| , and press CTRL-j but nothing happened. 
Overview ~
Getting Started
|usr_01.txt|  About the manuals
|usr_02.txt|  The first steps in Vim
|usr_03.txt|  Moving around
|usr_04.txt|  Making small changes
|usr_05.txt|  Set your settings
|usr_06.txt|  Using syntax highlighting 
|usr_07.txt|  Editing more than one file
|usr_08.txt|  Splitting windows
