There are currently 3 version of Win 8 (8, 8.1 and 8.1 update). You can learn which version you are using by following the directions on this site. If your Windows 8.1 update fails to install properly, Microsoft may provide you with assistance.
Full directions for obtaining 8.1 are available from PC Mag and Microsoft, or you can simply go here and tap "upgrade now." The full Win 8.1 can be downloaded.
Windows 8.1 is built for touch. There are a variety of touch gestures you can use to move around the screen. In addition, there is an introductory video and a more advanced video you can watch that will help you with using these touch gestures.
Here's an article that provides information about arranging your Apps on the Start screen.
Here's a video that will show you how to display two open Apps simultaneously.
You can learn how to use File Explorer to search for and copy files, as well as do many other types of maintenance projects.
Libraries were first offered in Windows 7. Here's a video that explains more about Libraries, and an excellent article that tells you everything you need to know about Libraries. Windows 8.1 changed how libraries work because the public folders are no longer included by default in the respective library. However, you can undo this change fairly easily.
Windows 8 includes two ways to backup your computer. There is an image based backup and a method known as File History. Here's an article that helps you setup the image based backup. If you want to use the File History method for for performing backups, there are three sites that can help you. Start with this comprehensive description of File History. If you still have questions about File History, they may be answered in this PC World article or the HowtoGeek article.
Windows 8.1 offers the File History method for backup and a different method from Win 8 for creating an image based backup.
Windows 8.1 comes with a number of pre-installed Apps. You can learn more about the People App, Mail App, Photos App, Music App, and OneDrive App. You may wish to download the web version of OneDrive or the Desktop version of OneDrive, both of which are more powerful than the OneDrive App. You can learn more about the OneDrive App here. You can also download Windows Live Mail, which is more powerful than the Mail App.
You can learn how to add photos to your App screen, Lock screen, or App background in Win 8.1
System Restore is a powerful feature that can help you fix a broken computer. Multiple versions of Norton Antivirus conflict with System Restore. You can learn how to overcome this conflict at this site or on pages 299-301 of this document.
Windows 8.1 comes with Windows Defender, a software program that provides free anti-malware protection. Free updates to Windows Defender are included. However, some computer manufactures disable Windows Defender and replace it with an alternative product. You can learn how to turn on Windows Defender, should you wish to do so. This article describes how to schedule automatic regular scans of your computer, using Windows Defender. (Scroll down in the article about 1/3 of the way.)
Windows 8.1 allows you to partially or completely restore your computer. This is different from System Restore, which is described above. You can learn more about these two options here or here.
Since Windows 8.1 does not have a Start button that leads to a traditional menu, it is more difficult to perform some tasks. Some 3rd parties have released software that brings back the Start button. Here are offerings from 9 companies as well as this one. One of the packages is called Start8. Here are the settings you should use for that program.
If you loathe the Modern User Interface, here's an article that explains how you avoid it almost all of the time.
Windows 8.1 does not come with the ability to play DVDs. This article will help you remedy the situation.
If you're accustomed to the Desktop and would like to avoid the Modern User Interface as much as possible, here's an article that can help.
Here's an excellent "cheat sheet" that lists many Windows 8.1 shortcuts.