Visit Shrine of the Trader in Moonstruck Coast. The shrine entrance is west of the save point here. Enter and press A on the shrine and achievement pop.
Moonstruck Coast is on the way to Alfyn’s Chapter 2 story. From Cobbleston, head northeast to North Cobbleston Gap, southeast to North Stonegard Pass, then north. Check the signposts if needed in each area.
I wouldn’t rush getting this or the other secondary job achievements as the areas have much harder battles compared to the starting areas for chapter 1. Be at or just a few levels below the “danger level” shown on screen when you enter areas.