Ragnarok Mobile Episode 7 adds the 4th Job Ascendancy to the job change progression system. Advancing will also unlock the new Origin Skill system.
You’ll need to be Job Lv. 80 to change to your 4th Job class.
Unlock 4th Job
First select your character portrait (top left), then switch to your class tab. Next select the “Job Change” button. You will be directed to Noen Vee in Prontera.
The quest chain is quite straight forward but varies from class to class. There’s the usual talking to NPCs and defeating monsters.
Base Level 140? Don’t forget to unlock Base Level 160!