First, you’ll need to make sure that your gradebook system account contains multiple students. If it doesn’t, you won’t be able to switch between students. (For assistance adding additional students to your account, you’ll need to contact your school or school district.)
If your account contains multiple students, you can switch between students by tapping the student profile icon in the top right of the app. This will bring up a selection menu to choose between the other student(s) in the account. Tap the desired student to start viewing that student’s grades/assignments/attendance/etc.