In order for you to join a class as a parent, you should add the name of your child who attends that classroom. Adding the child's name will show you as <parent of child> in your classroom. This will help other parents in the class know you as the parent of a child.  You can also add a child profile from your profile settings screen.

On Mobile - 

1. Click on All Groups on the left navigation tray. 
2. Click on your profile picture
3. Click My Profile
4. Click the +Child button below My Family 
5. Input Child's name, School and Activities
6. Click Save.

On Desktop - 

1. Click on your name in the left navigation tray (In browser)
2. Click your name
3. Click My Profile
4. Click the +Child button below My Family
5. Input Child's name, School and Activities
6. Click Save.