open up iTunes on your computer, drag the video you want to put on your iPhone to iTunes, or go to "files> Importe a file" and direct the dialogue box to the location of the video on your computer. If your video is not supported by iTunes, it might automatically convert it, (I'm not sure) or you will have to convert it into MP4 for iTunes to be able to place your video into it's library. Once that's done, connect your iPhone to your computer, highlight your iPhone in iTunes, select the videos tab, and check the video box, finally sync your itunes to your iPhone and voila. Good luck to you.