Every 1st of the month drop by a town and check the available dispatch missions. After doing that, travel around the world map and pay attention to the date. Then, you'll need to dismiss a bunch of your starting characters (you'll need to keep at least one non-story character, since story characters can't be sent on dispatch missions). play the story missions until the roaming clans show up, these are the rival groups that move around the world map. It's been a while but I think I can answer this.
