Вы можете использовать System.Windows.Forms.Help.ShowHelp(Control, String, HelpNavigator)
С MSDN
// Open the Help file for the Character Map topic and
// display the Index page.
private void Button2_Click(System.Object sender, System.EventArgs e)
{
Help.ShowHelp(TextBox1, "file://c:\\charmap.chm",
HelpNavigator.Index);
}