how does the narrator learn about Ethan Frome?

The narrator learns about Frome from Harmon Gow. Gow used to be a stagecoach driver and is well acquainted with town history (Starkfield). Our narrator has seen Frome at the post office and notices he's been badly crippled. Gow fills the narrator in on the fact that Frome had been disfigured in a "smash-up" accident, 24 years prior.