Locations and Roles can both be assigned to employees within their profile. To view an Employee profile, go to Company → Employees and click the name of the employee who's profile you'd like to view.
From there, you can use the Locations and Roles sections of the employee's profile to assign the employee to as many Locations and Roles as you need.
Both pages work in the same way - tick the boxes next to the Locations or Roles you'd like to assign. When you're done, click Save.
If you need to add new Locations or Roles to the system, you can do so by going to Company → Locations or Company → Roles and clicking the blue Plus button.