Using the code below I can get a page that doesn't require you to be logged in. But I need to be logged in to get the page I want..

How would I modify it to be able to use cookies to log in and retrieve the page?

What I eventually want to do is have a user and password input box on the form. Once the user clicks the button, it will grab the source and then manipulate it to how I want it.

Code:
        Dim wc As New System.Net.WebClient
        Dim html As String = wc.DownloadString("https://www.webpage.com")
        RichTextBox1.Text = html