Wake on LAN so cool, just want to write a iPhone app to WOL my PC, but have no idea to code, any one can point me the way?
If you've no experience of programming, then this is a very large first step. (More of a sheer vertical incline really.)
As such, you might want to take a step back and have a look a some basic (or indeed BASIC) programming tutorials. (Google is your friend.)
Alternatively, Apple has good online documentation regarding Objective C and the Cocoa (the language and framework that iPhone applications are written in.) A good place to start for this would be Apple's Introduction to The Objective-C Programming Language.
Basically you need to send a magic packed as described here, to do that you'll need basic programming knowledge and some knowledge on socket programming, here is a good book on the subject. There are numerous examples of that.
But in the end perhaps I could persuade you to purchase one of several iPhone applications that do exactly that, or grab the free one?
I know this is probably not the answer you are looking for, but why code your own when there's a few apps out there that do what you want?
Take a look here:
http://www.sk4.co.uk/
http://www.squidoo.com/turn-on-computer-from-ipod
http://bananaglue.de/wol/index%5Fe.php