Extend Android application

I need to extend my android application, but i don't have a time to do this. 1. Now my application generate and save file to the external storage (EXTERNAL_STORAGE/MYAPP). I want to allow the user to choose where he wants to save this generated file. 2. After this file is required, the app try to read the file which is stored in EXTERNAL_STORAGE/MYAPP by previous point 1. I want to allow the user to choose which file he wants to use. So i think this should be very easy.