How Do You Update Directions In Garmin Portable Gps Navigation System?

Are you asking about directions generated from the map sets? The answer is either “enter a new destination”, “change your routing preferences, so it honors your selction of uturns, avoidances, and transportation mode like foot vs. commmercial”, “get an updated mapsource from Garmin” (approx cost $75 USD)” if you’re looking for updated map data, or “upload a new route”.
Without more details in the question, it’s really difficult to be authoritative in the answer.