First, I note you prefer the Mepis desktop, but are you sure you have Kubuntu rather than Ubuntu, as there shouldn't be a lot of difference.
That aside, in Mepis, you need to click on the icon in the lower panel (task bar) that refers to "System". Then navigate to "Mepis" --> "Mephis Network Assistant".
Now click on Interfaces and check your wireless adapter is selected (could be something like ath0 or wifi0 and "Start at boot, Start when plugged and Use DHCP to get IP settings" should all be ticked. If your wireless details are all greyed out, the chances are it's because the wrong adapter has been recognised.
Now select the Wireless tab and select your level of encryption (or not) as the case may be. Make sure also, the "Frequency" box is ticked. It says it's optional, but I've found it needs to be ticked to make wireless work. Fill in the details as required.
Make sure you click "Apply" in each case.
Hopefully, you should now be able to use wireless, unless your computer has an oddball card that Mepis can't recognise. But I suspect that as Kubuntu can, it shouldn't be a problem.