The first thing you have to decide is if you are creating a fictional person with cerebral palsy, or if you are basing your essay on a case study or person you know personally.
If you are using a person you know, do a few interviews. Speak with the person directly to gain subjective descriptions and feelings, and incorporate those into the essay. Get quotes and accompany the person on a walk or other excursion to get their intimate reactions to other people and to their daily life.
If you are using a case study, gathering as much research as possible is important. Read the case study and imagine what the feeling is like at a personal level, not just at a descriptive level. Use strong descriptive words to highlight areas of difficulty and also areas of ease; differentiate between common stereotypes and the actual experiences of the person in the case study. For a fictional person, use the links below to research cerebral palsy and decide which parts to use; remember that cerebral palsy can affect different areas of function, and two cases may not be the same.
When writing the essay itself, focus on the subjective feelings of the person described, and compare those experiences with observed experiences; that is, look at others from the perspective of the person with cerebral palsy, and examine both the objective observations and the subjective feelings.
The most important thing is to use the most powerful descriptive words you can find. While the feel of an essay is partly in the format, a large part is in the language; common, ordinary words are not as effective. A thesaurus might be helpful.