Yes, you can deduct health insurance premiums for a dependent if you itemize and the total expenses for you, your spouse, and your dependents exceed 10% of your adjusted gross income (7.5% if you're 65 or older as of December 31, 2016). The deduction is limited to the expenses above and beyond this amount.
See Deducting Medical, Dental, and Vision Expenses
To enter your medical /insurance expenses -
Click on Federal Taxes (Personal using Home and Business)
Click on Deductions and Credits
Click on I'll choose what I work on (if shown)
Scroll down to Medical
On Medical Expenses, click the start or update button
See How much did you spend on insurance premiums? page.