Although you can set up an employee from HR too, it’s a different process / flow etc, so will belong in the Cintra People HR section.
There are two main categories here:
Add an employee to payroll (i.e. using the wizard)
Payroll employee details (i.e. what each of the fields mean)
General payroll employee related information like IR35 or auto-enrolment would probably be better as a glossary item, depending on how long the definitions might be.
Also, “Pensions” are quite complicated (e.g. this article https://cintra.freshdesk.com/support/solutions/articles/204000073668-employee-pension-membership) is quite long and goes into a lot of info about exclusion from auto-enrolment. These additional “concept” articles may merit their own folder (depending how many there are). Here’s another one: Identifying an employee as an off-payroll worker - Cintra Support