"Lights are being switched on"
zi- = subject prefix for class 10 (plural of the N class)
-na- = present tense
-wash(a) = ignite, light, turn on
-w(a) = passive voice
Combining the last two gives us the verb -washwa which means "be/get lit/ignited/turned on".
Niliwasha kompyuta. = I turn on the computer.
Kompyuta iliwashwa nami. = The computer was turned on by me. (nami = na mimi)
Helpful explanation yet again, but shouldn't niliwasha kompyuta = I turned on the computer, because it's past tense.