Companies are setup under:
Admin > Companies
Companies are configured in a hierarchy, with each company in the tree having a parent company.
The top-most company (typically the account holder) is the only company that does not have a parent.
This dictates the access of files within the structure. This allows you to create Affiliates of Affiliates.
Main Company can see the records of all companies including its own and that of those below it.
Affiliate A can see their own data, Sub-Affiliate A-A's data, Sub-Affiliate A-B's data and Sub-Sub Affiliate B-A's data
Sub Affiliate Company A-A can see their own data only.
Sub Affiliate Company A-B can see their own data and Sub-Sub Affiliate B-A's data.
Sub Affiliate Company B can see their own data only.
Sub Affiliate Company C can see their own data only.
This is done by selecting the "Parent Company" while editing or adding a company.
You can see what company belongs to what from the company listings page.