Code W in box 12 of your W-2 is the amount that both you through payroll deduction and your employer contributed to your HSA (Health Savings Account) in the tax year. Note that this amount is removed by your employer from Wages in boxes 1, 3, and 5 before your W-2 is printed - this is one half the reason that contributions to an HSA are a tax benefit, because you do not declare the contributions as taxable income.
Once you enter the code W amount on the W-2 screens, do not enter this amount anywhere else on the return - TurboTax will automatically carry this amount to where it is needed. Especially do not add the code W amount in the HSA interview as a "personal" contribution. A "personal" contribution to an HSA is considered by the IRS to be any contribution you made directly to your HSA, not through your employer.
Just enter the W-2 as indicated, and TurboTax will handle the rest.
As for importing your W-2 from DFAS, it is worth trying since TurboTax supports autoimport from a large range of companies (maybe even the Department of Defense); however, occasionally the auto-import does not work, so the workaround is to get a printed copy or see a display copy of your W-2 and then enter the values manually (i.e., don't enter the Employer's ID on the first screen for the W-2, but Continue to the next screen and enter all the information). But give the auto-import a try first.
