To access the new features you have to click the icon with the square, triangle, and circle in the upper right of an open Google Meet.

Once clicked you will be presented with a list of the new features. Clicking any of the features will open the window for it.

Breakout rooms allows you to create several rooms. You can assign students to different rooms or you can have Google shuffle them into the rooms. When finished you press Open rooms to start them.

A new update to Google Meet allows you to create breakout rooms in Google Calendar while creating a Meet. When the students arrive to your Meet they will already be in rooms. You can read more about that here.

Polls allow you to ask a question of the users in your Meet. The results appear after the Meet has ended. This option does not appear in the Meet app but does on the web based version.

You can ask questions of your Meet attendees by posing a question through the Q&A function.

Attendance is automatically taken when users enter and leave a Meet. The attendance is then gathered and sent to you in a Google Sheet to Google Drive. You will see their username, email, the time they entered the Meet, and when they left. For this to work properly you must turn off all the previous attendance extensions if you have them installed.

There is more information here.