Need help on transfer videos to Ipad 2

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Okay, I have done sync photo and E- book, and also mp3 file to my Ipad 2, now, the only left problem, and huge headache is sync the movies file. I followed the online instruction to convert any video files to mp4, which iPad will most likely to play; and all I have to do just drag and drop it to the movie category? Or simply import it to the library? I have tried the first one, drag the video files to Itune, but nothing happen, and I don't see any video files appear. I also tried import the file to the library, the same problem. So, how should I transfer a videos to Ipad 2 to watch? Please help!