See their guidance here ParentPay Guidance on usernames
ParentPay provides live online balance information to parents for dinner money, trips, childcare etc. It enables card payments to be made securely online, by phone or in person. This should provide better information and sheer convenience for parents and families. All payments made are fully receipted and in addition to a live balance, the system will provide a payment history. Thanks to everyone who has used the system to pay online We will be contacting parents that are not presently registered to use the system to support the activation of your account. Meanwhile feel free to contact the school office who will answer any queries.