You must arrange for two adults to submit recomendation forms on your behalf. One must be from a current or former science teacher. The second recommendation may also be a teacher (of any subject) but can also be a coach, club advisor, school administrator, or other adult who knows about your work ethic and achievements. You may not ask a family member or friend to write a recomendation for you.
You will need to send them the following link, which will be found in the confirmation page and email as well: http://www.lrsm.upenn.edu/outreach/pssi-let-of-rec-upload/