You may have received an email from your teacher inviting you to a Google Classroom. Clicking on the link in the link will add you to the class. These instructions are an alternate way of adding yourself to a class with a Class Code that may have been shared from the teacher
Click on the plus (+) symbol in the top right corner
Click on "Join class"
This will open a pop-up window in the center of the screen
Enter in the previously shared Class Code
Click on "Join" in the bottom right