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.
Sample Configuration:
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.