In order to be eligible to make a 2019 contribution to an HSA that doesn't exist yet in 2018, you have to have had at least one month of HDHP coverage in 2018. Part of the HSA interview in TurboTax is asking you which months you had what type of HDHP coverage in order to calculate the annual HSA contribution limit.
If you did not indicate any HDHP coverage in 2018, then all of your 2019 contribution would be in excess and subject to the 6% penalty. If your coverage did not allow a high limit, then any contributions in excess of that limit would be subject to the 6% penalty.
If I read your question correctly, you did not appear to have HDHP coverage in 2018, so you are not allowed to contribute for that year.
