Go to the Students Page
Select "Add Students"
Select the class you wish to add students.
You can either select students from a list that you have already added, or invite new students to the selected classroom.
If you invite new students you have the option to add students via a 3rd party like; Clever, Google Classroom, Microsoft Teams.
OR you can manually invite students via a code or the student's email. You can also Bulk Invite via a CSV or invite each student one by one.