This should have been reported on a code R 2018 Form 1099-R.  If your 2017 tax return did not already report the resulting traditional IRA contribution for 2017, either on Form 1040 line 32 (or Form 1040A line 17) or as a nondeductible contribution on Form 8606 line 1, you must amend your 2017 tax return to reflect the recharacterization.  If your 2017 tax return already reflects the recharacterization, you can ignore the code R 2018 Form 1099-R.