How do I add HSA contribution in 2019 for 2018 in turbo tax. I don't see a place to enter that value anywhere. Please guide with steps.

Type 'HSA' into the Search box in TurboTax, then click on  'Jump to hsa '.  

Then, you'll proceed with an interview that will allow you to make relevant entries.

tried that, it is only asking for information from 1099-sa and I want to add the I contributed in 2019 for year 2018 and that information is not in 1099-SA. I'm assuming this amount should show up in the deductions section.

When you enter your contribution amount, include the amount you contributed in 2019 for 2018.  If you'll go into "Forms" mode and then pull up Form 8889-T, you'll see that line 2 is supposed to include contributions made in 2018, and in 2019 before the filing deadline.