how to make browse button

You can use, FileOpenDialog control.
On click of a button, you can call FileOpenDialog.ShowDialog() to show the window where the user can select the xml file.
You can apply the filter to show only the xml files.
dialog.Filter = "xml files (*.xml)|*.xml|All files (*.*)|*.*";
Once the file is selected, you can use FileOpenDialog.FileName property to get the selected filename.

Use xmltextreader to read the xml file.
Form load event:
FileOpenDialog  fileOpenDialog = new FileOpenDialog();

Button Click event :
fileOpenDialog.Filter = "xml files (*.xml)|*.xml|All files (*.*)|*.*";
fileOpenDialog.ShowDialog();
XmlTextReader xmltextReader = null;

if (fileOpenDialog.ShowDialog() == DialogResult.OK)
{
   xmltextReader = new XmlTextReader(fileOpenDialog.FileName);        
    //you continue the xml processing....
}

Hope this helps you.