I am new to WSE and have been struggling with what I thought would be a
simple concept.  I have a web service called "Hello World".  All I want
to do is authenticate a user based on a username and password which I
will look-up in a database.  Can someone place outline the steps to do
this?  I've already created a CustomUsernameToken manager:

Imports Microsoft.VisualBasic
Imports Microsoft.Web.Services3.Security
Imports Microsoft.Web.Services3.Security.Tokens

Namespace MikeTest.WebService

   Public Class CustomUsernameTokenManager
       Inherits UsernameTokenManager

       Protected Overrides Function AuthenticateToken(ByVal token As
Microsoft.Web.Services3.Security.Tokens.UsernameToken) As String

           Return "thepassword"

       End Function
   End Class

End Namespace

What other classes/methods do I need to create/override to get this to
work?  The last error I'm getting is:
UsernameToken is expected but not present in the security header of the
incoming message.