I understand you are wanting to register your children online while inside of Unified Classroom. The Registration Forms are not housed directly inside of Unified Classroom just yet so in the mean time you will need to follow these steps to get to the Online Registeration Forms for your Children's District.
From inside of the Unified Classroom Dashboard click Quick Links
Then click on Main Portal Page
And this will take you back to the normal PowerSchool Parent Portal from here click on the Online Registeration Form on the left hand side menu
This will load you into the Online Registeration Forms which you can use to Register your children
I hope this information was helpful!