HELP! i cant manage to copy video files to my itunes library

im new to itunes and my ipad is my 1st apple product. i already converted the video files to to avi and .mp4 but they dont seem to copy to itunes when i drag them. i dont want to use any app with my videos , i already tried downloading an app so that i can transfer them and it works, but now i want to use the built in video app and transfer my files via itunes.. without using any addition apps in the market

when using itunes, no matter how many times i drag it over to my library or "add file to library" just like how i do it with my songs, they dont appear . please help