To setup the looks of the Desktop, just right click on the screen and choose "Change Desktop Background." Then choose whatever Theme you want. I prefer to choose the "Clearlooks" theme. Then click on the "Customize" button below and choose the "Icons" tab. Then choose "Humanity" (my preference) and close the box that it is in. To change to one of the built-in background pictures, click on the "Backgrounds" tab and choose the background picture of your choice. The one having to do with outer space is actually several pictures that will change periodically. You can also add your own pictures, if you wish. There are many variations of setup. There are even more than are given here if you wish to do a little research.
You should soon see the normal "Update Manager" window, that will periodically appear. Go ahead and install everything that it suggests. (Ubuntu will require your password to enable the updates.) Make sure your applications are NOT running when you do these updates.
For wireless connection to the Internet, a proprietary or "restricted" driver for your device may be offered. (In the upper right hand corner, for desktop installations, there is a small icon that indicates that you are either connected or not connected to the Internet. You can click on that icon.) You connect to the Internet as you would using a Windows program for your wireless device. However, for some wireless devices, the connection may not be automatic. You may have to manually enter the exact name (be careful with upper and lower case letters) of your home network, the type of encryption that you are using, and your password. It will generally want a separate password (or "name" that you wish to use) to identify the default network to which you wish to connect (generally your home network). Each time you connect, just type in that "name" and it should automatically connect.
With Ubuntu, you are given 4 separate screens (instead of just 1, like in Windows). In the lower right hand corner, you may select which screen you want to view. There are four icons representing the four screens in the lower right hand corner. You can also add or subtract from the number of screens available. (Just right click on one of the screen icons and choose Preferences.) If having 4 separate screens is confusing, you can change it to just a single screen as you would have in Windows.
For Advanced Users
Proprietary or "restricted" hardware video drivers may give problems to some computers. If a proprietary or "restricted" video driver is offered, it should be in a different notification window than the Update Manager window. You can also go to System→Administration→Hardware Drivers. If you want to experiment with it, first install it and enable it, and then disable it, to see which way the video is updated faster (such as less flicker when you watch a movie). (You may need to reboot each time you do this.) Even if everything works perfectly, the video driver supplied by Ubuntu may actually be faster for most videos than the manufacturer's proprietary or "restricted" driver. One of the reasons for installing a proprietary driver is that it may give your video card 3-D capability, that is, perform 3-D mathematical calculations for 3-D effects with some computer games.
Note for Other Situations (Including Boot Problems)
Occasionally Ubuntu will check your hard disk automatically. (This usually takes from a few seconds to a few minutes.) This does not mean that there is anything wrong. It is an automatic check.
I also advise that you connect electric power to your computer for a minimum of 60 seconds to 2 minutes before you attempt to boot it regardless of whether you are running Windows or Ubuntu. Many people also remove the electric power from their computer after they TURN IT OFF. I do that too, since my opinion is that it is hard on some electronic components to leave electric power connected to them all the time. Also, occasionally (perhaps if you boot your computer too soon after you have restored electric power to it), your computer may not be ready to boot that quickly and hardware malfunctions may occur (with some machines). If you have that problem while booting up into Ubuntu, wait until it appears to have fully booted, and then just do a normal shut down of the computer if you can. If you cannot do that, you may need to press the reset button on the computer (and perhaps remove the power from the computer at the very beginning of the reboot process).
When Ubuntu boots, if it says that it did not load an applet correctly and gives you the option to delete it, I advise that you do not delete it. Instead shut down your computer normally, remove the power for 60 seconds, restore the power for at least 2 minutes, and then reboot. Many times, this kind of rebooting will take care of such problems.