Adjustments to Income-Self Employed health insurance deduction

not knwing version yiu;re using. so instep bt step mode

federal taxes tab

wages and income

business items

schedule c - update

screen appears to edit or add. choose add only if you haven't started on schedule C

then click on continue icons several times until you get to screen for business info

thee check I'll enter myself

click on several more continues until you reach the business expense screen

then there should be a screen with lists a bunch of expenses which will include self-employment health insurance 

click on update all other expenses

note that the expense does not show up on schedule C but on schedule 1 line 16.