Hi Rana30,

Yes, you absolutely can!
Every user you create will create a contact which you can fill in as customer on the helpdesk ticket. If you just work with employees you won't have a contact out of the box. In this case you can just create a contact for every employee and then assign those contacts on the ticket.

If you really want to work with employees instead of customers you can add a field on the model 'helpdesk.ticket' where you add a Many2one to the model 'hr.employee':

class HelpdeskTicket(models.Model):
_inherit = 'helpdesk.ticket'

employee_id = fields.Many2one('hr.employee', string='Employee')

Regards,
Yenthe