Tenancies are assigned to control systems and profile schedules through grid view. Once you have created a tenancy, navigate to grid view. From the control system view you will see a Tenancy column and a dropdown. Changing the selected tenancy will update everything related to that control system to be accessible by all users who are assigned to that tenancy. All views will have a tenancy column stating what tenancy that row is assigned to if any.
Tenancies can also be assigned to profile schedules. You will see a similar tenancy dropdown column in the profile schedule view. This will assign the tenancy to that profile schedule and allow it to be access by users assigned to the specified tenancy.