The 2018 contribution to your Roth IRA is not reported on your Tax Return. However, you will want to enter the information in TurboTax to make sure you qualify for the contribution and because you may qualify for the Retirement Contributions Savings Credit (Savers Credit). You can enter your Roth IRA Contribution by following these steps: Where to Enter your IRA Contributions.
Keep in mind, a Roth IRA Contribution for you can't be in excess of your "earned income".
For example, if you made $3,000 at your job last year, you can't have a $4,000 Roth IRA contribution, the maximum contribution would be $3,000.
[Edited 3.14.2019| 2:26PM]
