YPN is different, they require you to have page views I believe. As for adsense, I think they look more for content than traffic, but I would apply to both and see what happens. As for wordpress, you have to edit your theme, you will see the button for it, in wp admin. I stopped using wordpress, so i dont know the exact location, but look for theme, then find edit. Then their will be file names (Like right sidebar, left sidebar, index, etc.) find where you want the ads placed, paste in the code, if its not where you want it, undo, and try again until it fits what your looking for.