Visit the Embassy to find the quest giver ( Stormwind / Orgrimmar). Older/main races may complete a quest chain to get their heritage armor (level 120 and exalted with their matching faction possibly additional requirements, depending on the race). Once earned, you can use this transmog on every alt of that race.
The ones of allied races require to level up one character of that race without a level boost (heirlooms are allowed) and gain the achievement (like Tradição dos Forjados a Luz).
