// Create an instance of the Tree provider first
    TreeProvider tree = new TreeProvider(CMSContext.CurrentUser);

    // get the node for testing purposue directly by it's node ID
   TreeNode node = tree.SelectSingleNode(1163); 

    if (node != null)
    {
            // Change coupled data
            node.SetValue("NewsTitle", "Title changed from code");
          
            node.SetValue("MediaSelectorColumn", "~/CorporateSite/media/Gallery/document.pdf&ext=.pdf");
        
// Save to database
            node.Update();
               
    }