If you added your students to a tracker by importing from SIS, any new students will automatically be added to your tracker when they are enrolled in PowerSchool.
It takes 24-48 hours after a student is added to PowerSchool for them to appear in your Mastery Connect tracker. The imports occur when PowerSchool runs its updates each night.
You cannot manually add students to a tracker if you previously imported the students using the Import Students from SIS option or the Import Students from CSV File option. As long as the student has a complete record in PowerSchool, the student will automatically import to your tracker.