Final answer:
Gloria needs to be aware of the program's location, the frequency of her attendance, and the duration of each session as these details are essential components of her Individualized Education Program (IEP).
Step-by-step explanation:
To prepare Gloria for the program, the three essential parts about her services she needs to know, which are also required on the Individualized Education Program (IEP), are the program's location, frequency, and duration. It is important for the IEP to specify where the program will take place, how often (or the frequency) Gloria will attend, and the length of time (or duration) of each session. These components ensure that the program is tailored to meet her individual needs and provides a structured framework for her educational services.