FolderBrowserDialog dialog = new FolderBrowserDialog();
dialog.Description = "Select path to synchronize to";
dialog.RootFolder = Environment.SpecialFolder.Desktop; // or whatever you like
dialog.SelectedPath = ...; // maybe set this to a previously selected folder
dialog.ShowNewFolderButton = true; // to enable the user to create a new folder
if (dialog.ShowDialog() != DialogResult.OK) return; // do what you need if user cancels the dialog

var selectedPathToSynchronizeTo = dialog.SelectedPath;