"You have two options. First, you can hold down the Alt key and
tap Tab to cycle between open apps, Windows-style. Second, you can
click the Windows List icon in the toolbar--it resides just above
the green power button.
"Want to install new software? Click Application Store in the
toolbar, then click the eponymous icon in the window that appears.
Here you can find GIMP, Picasa, Thunderbird, and countless other
programs (almost all of them open-source, meaning free). To install
anything, just click the corresponding green Install button."