To construct a copy of the angle \( \angle XYZ \) using ray \( YX \) as one of the sides of the new angle, after Isha has constructed the arc, the next step he must take is:
He must measure the distance between point \( Y \) and the arc using a compass.
This step will help him find the angle that is needed to duplicate the original angle \( \angle XYZ \). After measuring the distance, he can use this measurement to mark an intersection on the new ray that he will draw to create the required doubled angle.