Adding movies to iTunes

Since support for Apple iTunes blows I'll give you the answer.

Make sure your iPad is set to manually allow syncing:

By default, iTunes 11 and later manually manages your content on your device. Manually managing your device allows you to choose the content you want to have with you. This is useful if your iTunes library contains more items than can fit on your device.

You can’t manually manage music while using iTunes Match on your device.

Manually add items to your device

1. Connect your device to your computer.
2. Open iTunes. Make sure that you have the latest version.
3. Choose the content that you want to add to your device from your iTunes library.
4. Drag the content to your iPhone, iPad, or iPod. A panel should appear. Locate your device.

If you can't manually add or remove content from your device

Check to make sure that the "Manually manage music and videos" option is turned on:

1. Connect your device to your computer.
2. Open iTunes. Make sure that you have the latest version.
3. Locate and click on your device.
   
   
4. Click the Summary tab.
5. Click the box next to "Manually manage music and videos."
6. Click Apply.

You might see a message that your device is synced with another library. This means that you've used a different computer to sync your device in the past, and iTunes can't sync without first erasing and replacing all iTunes content on your device.

• If you're using an iPhone, you can only add music or video from a single iTunes Library.
• If you're using an iPad or iPod. you can add music from multiple iTunes Libraries, but video from only one iTunes Library.

SOURCE: Manage content manually on your iPhone, iPad, and iPod - Apple Support