From your 'My Hub' page (please see below)
If you go to the 'Menu' icon in the top right...
then select 'Groups' from the options
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'