When you open up iTunes normally you would expect to see iBooks library so that you could import eBooks such as PDF file into iTunes library, and from there you can transfer them to your iPad, iPhone or iPod. If you see this tab available, don't panic because you can easily enable it.
1. First launch the iTunes software.
2. Then click on Edit > Preferences menu.
3. Next click on the General Tab at the top.
4. Now under the Sources simply select the Books checkbox. While you are here, you can also enable any other sources that you want to use.
5. Click on OK to finish.
You should now see the iBooks available as a tab where you can select it to import eBooks.