In order to submit assignments and receive feedback on Kaizena, you'll need to join your teacher's group.
If your teacher has added to you a group using your email address or by importing your account from Google Classroom, you don't need to do anything: the group will show up in your list of groups on your groups page.
If you've been given a group code, you'll need to use this to join a group yourself.
When you log in, the first thing you'll see is your groups page. You can also go to your groups page by clicking here, or by clicking the groups icon:
Then, click "Join Group":
Next, enter the group code from your teacher (#1 in the screenshot below), then click "Join Group" (#2 below):
And that's it - you've joined the group! The group will show up on your groups page, and you can click it to open it. A private conversation will automatically be started between you and your teacher.