Question.  Why is there no help in the Mathematica Help Browser about a function you (Murray Eisenberg) defined?

Answer.  The Help Browser ordinarily includes help only about functions and other objects that are built into Mathematica or are part of standard add-on packages that are distributed with Mathematica. 

Other, third-party add-ons, such as David Park’s Cardano3 packages, sometimes come with Help Browser files, too.  If you install such packages for Mathematica on your computer, just select from the Help menu the item Rebuild Help Index.  That will merge the add-on’s help files with the Help Browser.

To see help about objects defined in such add-ons, including Cardano3, select the Add-ons & Links tab in the Help Browser.  Then find the add-on you want by browsing in the left-hand pane just below the tabs.

Functions that you or I define in Mathematica notebooks, however, are not built into Mathematica and are not in add-ons having accompanying Help Browser help.  So help about them is not available in the Help Browser.  That´s why, in the notebooks where I define such functions, I ordinarily include documentation in text cells and/or  usage message definitions that you may access with “?” in the usual way.  For example, if I define a function doit for you to use, and if I defined a value for doit::usage, then you could obtain help about doit by:

?doit

You can create usage messages for your own functions, too.  To create a usage message for your own  function myFunc, simply evaluate an expression like:

compositeQ::usage =
  "compositeQ[num] returns True if num is a\n composite integer, and False otherwise."