What if I have someone (i.e. vendor) that I want to have access to Namely Payroll but not HRIS?

You can set up an outside vendor with Namely Payroll access by going to Payroll > Company > Users and adding them in. That person will need to access Namely Payroll by going to https://namelypayroll.com. Upon initial login, they will need to click on Reset Password and create their password.