You do not have to have a PayPal account. Once at the PayPal page, see below the login option to use a credit card.
Use the first for competition registration per school:
Note that if your school was a paid member in 2016 and/or 2017, no new registration is due for 2018.
For individual student competition entries, use the form below, BUT ONLY if your school is not a 'member school'