I need help getting the username from the log in

I am a beginner.  So, if you respond to this post, please include as much detail as possible.

I am using VB.

I have a login script for members of my website.  The script is basically this:

 Sub LoginUser(s As Object, e As EventArgs)
  Dim blnAuthenticate As Boolean = Authenticate(username.Text, password.Text)
  If blnAuthenticate Then
   FormsAuthentication.RedirectFromLoginPage(username.Text, False)
  End If
 End Sub

 Function Authenticate(strUsername As String, strPassword As String) As Boolean
  Dim objConn As New OleDbConnection(ConfigurationSettings.AppSettings("DSN"))
  Dim objCmd As OleDbCommand
  Dim objDR As OleDbDataReader
  Dim userFound As Boolean

  objCmd = New OleDbCommand("SELECT * FROM Logins WHERE Usernames='" & strUsername & "& ...