The amount of HR users you are allowed is dependant on your plan size.
When you set up an account the Admin will automatically be assigned as one of your HR users.
From there you can assign other members of your team to have HR privileges.
If you are not looking to upgrade your plan we offer the option to purchase an additional 3. This can be done by going to Configure > Plan and Billing > Change plan
To find out more about User Permissions please click below.