You need to install iTunes on your computer, not the iPad - your iPad already has an iTunes Store app on it (for browsing the store and buying/downloading media), that is the only iTunes app for your iPad.
To sync content from a computer to the iPad you need iTunes installed on the computer. You don't have iTunes installed on that computer, that is the computer that you sync to ? If not are you going to want to sync other content e.g. music, films etc - if you do then there are some steps on this user-tip for syncing to a new computer : Syncing to a "New" Computer or replacing a "crashed" Hard Drive
To copy a powerpoint file to your iPad you need an app on your iPad that supports that type of file (iPads don't have a file system like a computer, everything is stored in apps). To get the file from your computer to that app you might be able to use the file sharing section in iTunes (About File Sharing on iPhone, iPad, and iPod touch - Apple Support ), or email the file to yourself and use 'open in' in the Mail app on the iPad, or use DropBox, or copy it via your wifi network - different apps support different transfer methods.
(I've asked for your post to be moved to the Using iPad forum, where you've posted is for questions about the iTunes U app.)