Your contributions have already been deducted from your income- your W2 box 1 reflects this pretax benefit. You can only deduct HSA contributions on your tax return if you made additional (allowable) contributions outside of your employment (which is unlikely).
You do need to enter the Code W, but keep in mind the reporting of this is not so you can deduct a contribution which has already been deducted. Its so you can complete the Form 8889 to verify your eligibility to have an HSA in the first place.
Both your employer and your contributions for an HSA go into Box 12, Code W. Box 14 is informational, and should not include HSA contributions. The Box 14 may be your health insurance, which has also already been deducted to arrive at the figure in Box 1 of your W2. What's the Box 14 description that you see?
Visit the HSA section after entering your W2:
- Federal Taxes
- Deductions and Credits
- Medical
- 1099-SA, HSA, MSA
