I was twelve years old. For me, it was a combination of (a) reading Creem magazine, (b) listening to Dr. Demento's syndicated radio show, and (c) some of the more accessible "new wave" bands were starting to make minor inroads that year (1979).
I should also add that I was a fan of 50s and 60s rock, thanks to oldies radio. Punk and new wave, to me, sounded like a return to those bygone eras. Looked like those bygone eras, too. At a time when the typical rock star looked like THIS:
...the typical punk rocker looked like a throwback to the Monkees:
^^^This may appear to be standard rock star attire now, but for the mid-late 70s, hair this short looked almost stark.