On the bottom of the screen you find the desktop panel. You use the panel to launch applications. Have a look at the button on the left with a large K. This button is called the Application Starter. It has a small arrow on the top to indicate that it will pop up a menu if you click on it. Just do it! The popup offers you easy access to all KDE applications installed on your computer system.
Shortcut: Alt-F1 opens the Application Starter menu.
If you use one application or tool very often, then you may want to have even faster access to it, of course. In this case, you can add a single application or an entire sub-menu of the Application Starter menu as a special quick-launch button onto the panel. If you want to reach the "Find Files" directly via a launch button, simply choose application starter > Panel > Add Application > Find Files (By this we mean that you should first click the Application Starter, then select "Panel" where the small arrow to the right indicates that another menu will pop up. In this menu, choose "Add application" and in the next sub-menu, "Find Utility".). Note that you can move all items of the panel around with the "move" command of the context menu. Just click with the third mouse button (the third mouse button is normally the right button, but if you have configured your mouse for left-handers e.g., it might also be the left one). A menu will pop up where you can choose "Move". Now move the mouse and see how the icon follows while still staying on the panel. When you are done, simply hit the first mouse button (by default the left one). As you have may have noticed, there is also a menu entry "Remove" in case you are tired of a certain launch button on your desktop.
This leads us to another interesting topic: in many places, you can click the right mouse button to display a context menu with choices that are applicable to the item you clicked. It is therefore always a good idea to try out the third mouse button on something, if you do not know what to do with it. Even the background of the desktops has such a menu!
There are other interesting things possible with the panel. One may be important if you have a low resolution on your monitor: it is the "hide-and-show"-function, activated by clicking on the textured bar on the left edge of the panel. By the way, if you are not sure what a certain button does in KDE, just move the mouse pointer over it and wait for a short while: KDE has a built-in mini context help, called "tooltips", which explains the functionality of such controls in a few words.
Just calm down, there is nothing to fear. KDE does not want to take your beloved (and sometimes very effective) command line away from you. You can move your files with the desktop, but you can also use the Unix commands you are accustomed to. KDE provides a very sophisticated command line window called kvt. Choose application starter > Utilities > Terminal to start it. This may be something you want on your panel!
Sometimes, you only want to enter one command on the command
line. In these cases, you do not need a full-blown terminal. Just hit
Alt-F2 and you get a small command line where you can enter one
command. The command line window will disappear afterwards, but it
remembers your command. When you pop up this window (which we call
"minicli" by the way) and hit the Up-arrow, you can browse through
all the commands you have previously entered. Also, you can enter URL's
in minicli to open a kfm window with the specified URL.
A final tip: to display a Unix man page, enter man:command
in minicli, where command is the name of a Unix command.