Hello im having a hard time dealing with phonegap 3.4.0 file system api.

Im developing an ios application, in the www folder i have an imgs folder which have like 16 pictures. I can write their names like this but I want to access those files urls dynamically with phonegap api. I have tried every tutorial but all of them didn't work. I dont quit understand how phonegap file system works. Can I accsess files on the www folder with phonegap api? if not where should I put the files in xcode, in which folder? and how can I get their url and use them in my project??!! like listing all the files in a folder on some other file than www. but also I need to know in which folder should i store my files? can some one help please? Im so confused ;( phonegap file docs are so confusing