how do I remove content from my IPAD?

Go to Settings>General>Usage>Storage. You will see all of your apps in there. You can tap on the app and you can delete it in the next window - if that is what you really want to do.

You can also unsync content with iTunes and keep all of your purchased content in iTunes on your computer, rather than deleting it all and having to download it again.

You can transfer all of your purchased content into iTunes, then deselect the content that you want to remove, and then sync with iTunes to remove the content that you deselected.

Transfer purchases.

http://support.apple.com/kb/HT1848

Go to General Settings and to usage. Now it should display the apps and there space. Click on the app, and then Delete app. To delete content inside apps, like books in the iBook app, you press and hold on the content until it wiggles. Press the x button next to it.