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You can refer to this article, How do I log into PowerSchool, to setup up the Parent Portal account. This quick guide: Student and Parent Portal Quick Start Guide to help you access the Parent Portal.
The unique access ID and Password help link students to the Parent Portal account and is provided by the district. It is not the same as the Parent Portal credentials. You will need to set those using the Create Account button on the Parent Portal page. You can refer to this article: Adding Students to the Parent Portal to add a student to your Parent Portal.
In case you are using the PowerSchool SIS Mobile App, this article: Using-the-PowerSchool-Mobile-App, should guide them on the process to link the Parent portal.