MyMPx.org - How to download themes and get them to work on nano clone?

I am sorry if I am bothering anyone with this question, I don't think it has been answered. I have a 1.8" nano clone, looks exactly like a Nano, works great but I would really like to download one of those Ipod look alike themes, but don't really know what I am doing, and don't want to screw it up. Is there possibly a detailed guy that some one has written that explains how to do it. If there isn't, to those that have done it, is it simple? My mp4's firmware is ACT_V3.5.35, thats all it says, that and the serial number. Does the firmware mean anything? To anyone that helps me thanks. Your help would be much appreciated, again I am a noob to downloading firmware and getting it to work.