Box 12 of my W-2, shows that I elected to put $3300 dollars into a 401k. Later, when asked if I put any money into a 401k in 2016, I entered this same $3300. Correct?

Was the follow up question about IRAs (not 401ks)?

There is no place in TurboTax that asks you to enter this amount other than in box 12 of TurboTax's W-2 form.  Do not enter it anywhere else.  (A 401(k) is not an IRA.)