With Google Classroom, you can join your class in three different ways:
Open your email account.
Click the class link shared by your teacher.
Select the account you use for the classroom.
Note: If you need to switch accounts, click Switch accounts before you try to join
Go to Google Classroom and login using your existing credentials.
Click on the Plus icon at the top right and then select Join Class from the pop-up.
Paste it below Class Code and then click on Join at the top right. You’ve successfully joined the classroom.
Open the class card and click Join.