for this first create a windows application.name it help
place a button in the designer and set the text-show help.
now double click on the button and write the following
code the the code file-
Help.ShowHelp(Form, @"d:\Helpfile.htm");

or you can also define a parameter-HelpNavigator.this
will specify which elements to display from the help file.
you may also define a keyword to search for.a example
follows-
Help.ShowHelp(Form, @"d:\HelpFile.htm", "Topic");

the HelpProvider component lets you specify control help
on form.this HelpProvider,an extender provider-maintains
properties for every control added in the form.you may
define a HelpString for every control on you form.

this string is shown whenever the focus of the control is
active and f1 is pressed.you may also define a HelpNameSpace
which defines the Url for the file of help related with
HelpProvider.

some properties are HelpString,HelpKeyWord,HelpNavigator.
you can set these properties for this component.