How to transfer pictures from my computer to my iPhone 4?

I'm not talking about putting pictures that I took with my iPhone 4 onto my computer. That is very simple, and I've done it multiple times. What I can't seem to do is transfer pictures from my computer to my iPhone.

Email them from your computer to your phone

You have to set it up in iTunes
I added the support link below.

http://support.apple.com/...kb/PH12316

You have to sync your photos from the PC using iTunes. All the pictures have to be in the My Pictures folder, but you can change the location: just open iTunes & connect your iPhone to the PC using the USB cable (or firewire). Click on the right corner, you gonna see the iPhone. That opens a Special menu JUST MAKE SURE THAT nor "music" nor "applications" nor "videos" etc is checked ONLY PICTURES HAVE TO BE SELECTED. After that, just click "Sync" or "Apply Changes" and all your pictures gonna be on your iPhone. Don't forget uncheck the "pictures" option when you're done. Or keep all your pictures on "My Pictures" to prevent that the iPhone will sync it again and lose all.

Thought of using a USB drive? You could use that to put the pictures on your phone.

hope that helps. ^^