Hello,
As of time of your writing, version 1.2.2 was still the most recent one and it's be pretty challenging to set permissions by yourself in that version.
However, version 1.3 that just came out yesterday has integrated permissions editor and using this tool you can adjust who has access which records. The tool is quite powerful and may require some getting used to, but I an assure you it's worth a look. We have plans to include a short manual soon as well.
You can find the tool logging on your EPESI installation, going to Administration, Record Browser and switching to permissions tabs. Remember to select the right recordSet to work with. For your particular solution, I think you'll find the module 'Account Manager' very useful - it add a new field in Companies, to which you can assign Salesman who works with this company.
Hope this helps,
Arek