iphone存储然后从Documents文件夹中读取文件

this must be easy but I want to put a file in the Documents folder which is read in at start up. I have the code on how to read and have confirmed its looking in the correct directory. However the file I have ,RootList.txt when saved in the Resources folder in xcode, is stored under the Root.app folder and the Documents folder is empty. Therefore its not finding this file when I start the app.this must be easy but I want to put a file in t