The place to change jobs to an Archer is located in the Mountain Vilage Payon. In the Archer Village, visit the Guildsman inside the Archer Guild. In order to raise concentration and patience, the test consists of gathering Trunks. By hunting Willows found near Payon, you gather a certain amount of Trunks and once they are turned in, you will be able to change jobs to an Archer. Job Lv 10 and higher is required.