A Business Group can be compared with an Organization in vCloud Director. A Business Group could be for example a group of people in Dev, in Production and so on.
A prerequisite to a Business Group is a prefix. A prefix is required and effectively is a set of characters followed by the virtual machine name.
For instance – if your Prefix is ‘vra7-‘ – your virtual machines will have the virtual machine name ‘vra7-vmname‘
Navigate to Infrastructure > Administration > Machine Prefixed
Click New
Here just enter a prefix (name), the number of digits and what the next number will be.
Click 
Now time to create the Business Group
Navigate to Administration > Users & Groups > Business Groups
Click New
Give it a name and and email address
Click Next
Add the admin and user roles. The Support Role is required if you want to give a group permissions to deploy workloads on behalf of someone. Doesn’t apply in my environment.
Click Next
Select the newly created Machine Prefix
Click Finish
Now you can create your reservations.