Hapara is not automatically rostered from Infinite Campus. You can roster a Hapara class by syncing with Google Classroom . Here is a video. This video will also show you the "Sync Class" button in Hapara to re-sync with Classroom in order to add/drop students who were added/dropped in Classroom. The basic steps are also outlined below:
Click “Sync Classes”
Choose your Google Classrooms to sync then click “Add Classrooms”
A Hapara classroom will be created using your Google Classroom roster.