Once a group is created, you can create sessions (meetings with your attendees) to take attendance. To create a session you need to be inside a group.
There are two ways to add sessions to your group:
Add a single session
Add multiple sessions as per a weekly recurring schedule
Add a single session
Navigate to the group
Tap the + button
Add button inside a group
Tap Add a new session
Add a new session on the group page
You can either start an ad-hoc session on the fly or schedule your session at a predefined time and venue:
Add details of a new session
Enter details as per your requirement.
Your session will now be created to take automatic attendance. It will show up on the group timeline.
Add multiple sessions as per a weekly recurring schedule
If your sessions follow a weekly schedule:
Go to the group page
Tap the + button
Select Add by a weekly schedule

Add by a weekly schedule option
On the next screen, enter your weekly schedule

That's it! Once you enter your weekly schedule here, all your sessions will be created accordingly.