Copying Wallpaper from MBP to iPhone...

I've downloaded some nice wallpapers to my MBP (Lion) that I want to transfer to my iPhone (3GS) and use as wallpapers. I've connected the 3GS to my MBP via the Apple cable and somehow, fumbling and stumbling, managed to copied the iPhone photos to it. Don't ask me how I did it. I still don't know. But I'd like to do the opposite and transfer the wallpapers from my MBP to my iPhone. How do I do that?

Be kind. I'm rather new to Apple.

Thanks,
AliOop

The easiest way:

1. Copy the wallpapers into iPhoto. You do this by dragging and dropping them into iPhoto's main window.
2. (tip) Put the wallpapers into their own album.
3. Close iPhoto, open iTunes, connect your iPhone, visit the "Photos" tab and choose your "Wallpaper" album to be synced.
4. Sync.
5. Now, on your iPhone, open your Photos, select the wallpaper you want, press the action button (square with an arrow pointing right) and choose "set as wallpaper."

aaannnddd ... DONE!

Thanks. I'l give it a go.