Hi friend;
Do not confuse employees and users
For OpenERP, “employee” (hr_employee)represents all of the physical people who have a work contract with the company. This includes all types of contracts: contracts with both fixed and indeterminate time periods, and also independent and freelance service contracts.
A “user” (res_users)is a physical person who is given access to the company’s systems. Most employees are users but some users are not employees: external partners can have access to parts of the system.
So, to make a user an employee in your company, you should add some settings in the access right control (ACL).
Check those links:
http://useopenerp.com/v8/model/res-users
http://stackoverflow.com/questions/22189332/how-can-i-setup-user-roles-in-openerp
Regards.