Creating a new tab

Im currently making a tabbed note pad, im stuck on the tab part, heres my code so far....\
Im using the DotNetBar tabcontrol, Im using Visual Studio 2010.
And how would i go about opening the .rtf or .txt files through the context menu in the PC?

Code:

---

Dim rtb As New RichTextBox
        rtb.Dock = DockStyle.Fill
        TabControl1.CreateTab("New Document")

---

Taabcontrol :

http://msdn.microsoft.com/en-us/library/8fb09fh2

Open Files :

http://msdn.microsoft.com/en-us/libr...5%28v=vs.71%29