Thanks for the help.
To help others, this should then be the final procedure.
Public Sub SetChannelInfo(Game As String, Status As String)
Try
Dim myReq As HttpWebRequest
Dim myResp As HttpWebResponse
myReq = HttpWebRequest.Create(Twitch_BaseURL & "channels/" & Twitch_UserID)
myReq.Method = "PUT"
myReq.ContentType = "text/plain"
myReq.Headers.Add("Client-ID:" & Twitch_ClientID)
myReq.Headers.Add("Authorization: OAuth " & My.Settings.Twitch_AuthenticationCode)
myReq.Accept = "application/vnd.twitchtv.v5+json"
Dim myData As String = "channel[status]=" & Status & "&channel[game]=" & Game
Dim Buffer As Byte() = System.Text.Encoding.UTF8.GetBytes(myData)
myReq.GetRequestStream.Write(Buffer, 0, Buffer.Count)
myResp = myReq.GetResponse
Dim myreader As New System.IO.StreamReader(myResp.GetResponseStream)
Dim myText As String
myText = myreader.ReadToEnd
Catch ex As Exception
MsgBox("Some error on setting Channel Info")
End Try
End Sub