'Make sure you import "Imports System.IO"
Dim openFileDialog1 As OpenFileDialog
If OpenFileDialog1.ShowDialog() = System.Windows.Forms.DialogResult.OK Then
   'declaring a FileStream and creating a document and access mode
   Dim myfilestream As New FileStream(OpenFileDialog1.FileName, FileMode.Create, FileAccess.Write)
   'creating a new StreamWriter
   Dim s as new StreamWriter(myfilestream)
   'writing text to file
   s.WriteLine("Write Some data here!")
   s.WriteLine("Write Some More data here!")
   s.Close()
End If