If you check the output of
$ echo $PATH
You will notice that /usr/local/kde4/bin is not listed. Thus, when you try to run KDE4 commands from the shell, they will not be found. The shell looks in each directory listed in $PATH.
If you want to start KDE4 commands from the shell, then you need to add /usr/local/kde4/bin to your path. And then you need to tell your shell to update it's internal cache. How you do that depends on the shell you are using.