The line for a contribution to your HSA made directly (i.e., not through your employer) can be found on Schedule 1 (form 1040). It's still line 25 - as you can see, a number of additional income items as well as the adjustments to income were moved to Schedule 1 during the redesign of form 1040. Please see https://www.irs.gov/pub/irs-pdf/f1040s1.pdf .
