E-filing of EAD and AP

I just filed EAD and AP application on line. I wonder if I need to submit any other supporting documents by mail. For example, on the I-131 form, it is required that "on a separate sheet of paper, please explain how you qualify for an advance parole document...". Do I need to mail a letter explaining that? Do I need to send photos? Anybody having got your EAD and AP, please help. Thanks.