iOS: About File Sharing
Using iTunes 9.1 or later, you can copy files between your computer and apps on your iOS device that support File Sharing (for example, Pages for iPad supports File Sharing, so you can create a document in Pages on your iPad, then copy it to your Mac so you can open it in Pages for Mac OS X). This article explains how to copy files between your computer and your iOS device using File Sharing.
What have your tried?
What was the error message?
What computer do you have? What version of iTunes?
You may want to try dropbox.
A simple and popular way to copy files and share files amoung your devices.