Android : create a text file(accessable from file manager)and insert strings in that

i need to create a text file(accessable from file manager)and then insert strings in that,how can i do that? i have below code but i can't access text file from file manager:

    private void writeToFile(String data) {
    try {
   OutputStreamWriter outputStreamWriter = new OutputStreamWriter(openFileOutput(FNAME, Context.MODE_APPEND));
        outputStreamWriter.write(data);
        outputStreamWriter.close();
    }
    catch (IOException e) {
        Log.e(TAG, "File write failed: " + e.toString());
    } 

   }
   }