"A lányok megcsókolják a fiúkat."

Translation: The girls kiss the boys.

[SedatKlc]

why do we add meg- before the verb?

[96314081311257]

I think it conveys some kind of perfect aspect (?)

I don't know much about aspects, but as a Hungarian native speaker, I'd translater the version without meg- as "The girls are kissing the boys."

[Tielbert]

Is meg- making it continuous or one-time? Are they kissing now or they kiss them usually?

[quaid_]

It translates better to "The girls are kissing the boys," so continuous I think.