I download some video from a tutorial site into ituens in my windows 7 pc. now i want to see those videos in my ipad. How can i transfer all videos into ipad?
The official way would be to do it through iTunes.
Add the videos to iTunes then connect your iPad to the PC, in iTunes select your device, go to the movies tab, then select the videos.
If this doesn't work because the videos are not supported.
Use an application like good player to manually add the videos to the app. follow the app's procedure.
Through iTunes anyway
If your video format is not supported but you want to use the official way, you will have to convert the videos using applications like handbrake first. Then you will be able to add them through iTunes.
If it isn't in a format that iOS/iTunes handles you need to convert it first. One very nice tool i Handbreak available for both Windows, Linux and Mac. It has preconfigured settings for alot of different devices.
After converting the video, drag i into iTunes and then sync it with your iOS device.