If you spent any money out of your HSA (typically for qualified medical expenses), then your HSA administrator (not your employer) is required to send you a form 1099-SA reporting on the distribution.
Yes, they should have sent it by now - unless you had no distributions in 2018, in which case you will not receive the 1099-SA. In this case, in TurboTax you would just skip entering it.
If you took any distributions from your HSA in 2018, go to your HSA administrator's website and see if your 1099-SA is available on their website, or call them and ask where it is.
