Well, first you need to de-brand your phone using setool2lite, and then you add the themes with xs++. When I went to debrand my phone (which is also a w580i) I watched this video on youtube:
YouTube - How To Debrand/Fix The Screen On w580i --it has the files you need in the info. Then I watched this video to find out how to put themes and menus on my phone:
YouTube - How to Get Flash Themes and Menus on W580i. You will need the cable that came with your phone (The gray one that connects you phone to a PC.) Hope this helps....P.S. -it's worth it!