You can adapt the basic message to take into account your employer/school/college needs. You should try and set up an appointment to tell the necessary people or call them aside for a private discussion. State you have epilepsy in a direct, factual way. Follow this with words of reassurance, giving information about how your epilepsy does or doesn't effect you at work/studies. If you want, you can offer references from previous employers or your consultant/GP about your epilepsy and how it relates to your work.
I would just put it quite simply – I have another matter I have to mention to you, I actually have epilepsy. I may experience an occasional seizure, it's nothing to be concerned about, it can easily be controlled in that regard, and there are things which we can follow. I can bring information to you, there's plenty of information, there's contacts I can give for you as well. So if you have any further questions for me.
I suffer from epilepsy, and it's as simple as that and I've just certain requirements that I need when I come to exams. Or I might have a case where I won't get an assignment in on time if something goes wrong, and it would have been just a very ordinary conversation.