Here's a simple how-to on restarting services in KDE. I will be alluding to this article in other guides on this site, rather than repeating myself every time - Lazy organisation, I call it :)
OR
You can do this in double quick time via the command line by typing the following:sudo /etc/init.d/[service name] restart
where [service name] indicates the service you are looking to restart. Similarly, you can also stop and start services by using the stop and start keywords respectively instead of restart.
Hope this helps!