Normally each sales person is a "User" of the ACT database (i.e.. they can log in with their user name). What then happens is that you change the Record Manager field (in the Contact info tab) to the name of the sales person responsible for that client.
Their name will then be associated with that client for reporting purposes.
If you want to "hide" Sales Person A's contacts from Sales Person B then you need the Premium version as previously stated.
