To add widgets to the desktop, Right-click on the desktop and choose Add
Widgets. A panel will appear at the bottom. Scroll though and choose one
and drag and drop it in place. To add then to the panel you right-click on
the panel. This will only work if you click on a spot on the panel that is
not already occupied. Widgets can be moved and removed once they are added
by clicking on the widget. To configure mouse over it and click on the
wrench. To resize mouse over and click on the resize icon. To remove
right-click and choose Remove widget. To move it mouse over and grab on the
popout bar.

KDE is very powerful and versatile, but you can mess it up if try to change
it too much without practice. If it does mess up you can start over by
just deleting the hidden folder .kde. It will rebuild itself from scratch
after you logout and back in.