Rental income is reported on Schedule E Supplemental Income and Loss which requires TurboTax Premium Online version.
If your return has been transmitted and accepted by the IRS, you may amend your Federal 1040 tax return.
If you used TurboTax Online, log in to your account and select Amend a return that was filed and accepted.
If you used the CD/download product, sign back into your return and select Amend a filed return.
See also this TurboTax Help.