From your 'My Hub' page (please see below)
On the left hand side of your account, you will see the side menu in which you can select 'Groups'.
This will then show any groups you have created
By clicking 'Create Workout Group' at the bottom of your screen
You will be able to create a workout group
And once created you can simply select the group to add any workouts by clicking 'Manage Workouts'