You should have gotten a Form 1099-R for the distribution from the old IRA. You just enter it in TurboTax like any other 1099-R, and proceed through the questions. If the 1099-R does not show that it was a rollover, after you enter the 1099-R TurboTax will ask you if you rolled it over.
If you did a direct trustee-to-trustee transfer (which technically is not a rollover) they might not have issued a 1099-R. In that case you do not have to enter the rollover on your tax return.
