It's good that you already took your 2017 distribution in 2018. If 2017 is your first year for which RMD was required (meaning you turned 70 1/2 in 2017), the deadline for taking 2017 RMD is April 1, 2018. If that's the case, it is not late and no special reporting is required on your tax return. Also, be sure to take your RMD for 2018 by December 31, 2018. These distributions will be taxable on your 2018 tax return.
If you turned 71 or later in 2017, you will need to complete form 5329 to request a waiver of the 50% excess accumulation penalty on the late 2017 RMD. If you have any form 1099-Rs included in your tax return, you can do this through TurboTax by indicating that you did not receive all the RMD for 2017. This will cause TurboTax to prepare Form 5329 where you can request a waiver of the 50% excess accumulation penalty on the late-taken 2017 RMD.
If you have no other 1099-Rs, you will have to complete the form 5329 outside of TurboTax. This will also mean that you must mail your tax return in. Please feel free to post any additional details or questions in the comment section.
See the link for a copy of form 5329. https://www.irs.gov/pub/irs-pdf/f5329.pdf
