Each kiosk you purchase requires a service account which can then be configured further I the Attendance Setup area.  

Go to Sentral Setup Cog > User Accounts > Manage Service Accounts.  

Service Accounts are a special type of user account which are designed to be used for specific designated functions. The most common example would be for a dedicated student attendance kiosk, which requires a user account for logging on to Sentral and audit logging purposes but should not have any access to other parts of the system.