Step One:

Access your student classrooms when you login using the link below.
https://classroom.google.com

-or- 

By signing in at Google.com and choosing Classrooms from the grid menu located in the top right of your browser. 

Student logins start with their HS graduation date and include first initial plus last name.
Example: Grad Year 23 John Smith = 23jsmith

---

Step Two:

If you have not yet accepted your Google Classroom, click "Join" on your classroom tile.