Q: how to put music videos on itunes stored on libary

Did you already go through these FAQ's? Videos have to be added to the iTunes library first:

Frequently asked questions about viewing and syncing video with iTunes and iPod

Why can't I transfer videos to my iPod?

If you have the media on your iPod and want to transfer them to iTunes on your computer, connect to iTunes on the computer, right click on your iPod in the device list and choose "transfer purchases"