I use this code to replace word file's some words with vb.net windows application text boxes values.

 'use early binding
        Dim objWordApp As Word.Application = Nothing
        Try
            objWordApp = New Word.Application
            'Open an existing document.

            objWordApp.Documents.Open("C/temp/word.docx")
            'copy data to clipboard
            txtFirstName.SelectAll()
            txtFirstName.Copy()
            'find <address>
            objWordApp.Selection.Find.Execute("<address>")
            'copy richtext from clipboard
            objWordApp.Selection.PasteSpecial(DataType:=Word.WdPasteDataType.wdPasteText)
            'clear the clipboard
            Clipboard.Clear()
            'Save and close the document.
            objWordApp.Documents.Item(1).Save()
            objWordApp.Documents.Close(Word.WdSaveOptions.wdDoNotSaveChanges)
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        Finally
            'quit Word
            If Not IsNothing(objWordApp) Then
                objWordApp.Quit()
                objWordApp = Nothing
            End If
        End Try

But Now I want to open and select word file by open file dialogue. Currently I coded where word file located.
And also want to save new edited word file to other location by save file dialogue. Can anyone help me ?

The classes involved are OpenFileDialog and SaveFileDialog. Basically instantiate a new instance of each class and use the ShowDialog() method to show it. The Filename property contains the filename opened, or saved.