Step 1: Add Attendance as an Activity
Add the attendance activity to your page 
Step 2: Create a Session
Create your sessions by going to "Add Session" tab.
Select date and time of your class
If you wish, you can create a calendar event for your unit (optional)
Step 3: Create Multiple Sessions
You have the option of repeating these session depending on the frequency of your class
For example: Repeat on Monday every 1 week(s) until: then select a date for the final class of term
Step 4: Student Recording
Tick the box "Allow students to record own attendance"
Tick "Random password" (optional)- this will also generate a random password for you to share with your students in class
Tick box "Include QR code"
Click on "Add" at the bottom in the blue box
Step 5: Your Session QR Code
You will now see your sessions have been created along with a QR code icon as shown below

When you click on the QR code icon, a student password will appear as below

Click on "Show QR Code" and the full QR Code will appear that you can share in class for students to check themselves in for class attendance.