If a Contact is an Account Owner, the Contact has access to view and edit the Account information and view all Files associated with the Account.
If a Contact is not an Account Owner, the Contact does not have access to view or edit the account information and only has access to Files that have been tied to their Contact.
To assign Account Ownership:
1. Navigate to an Account
2. Click the Contacts tab
3. Hover over a Contact
4. Click Edit
5. Check the Account owner? box
6. Click Update