I replaced the fence and HVAC this year on a rental property that was put in service in 2018. How do I enter this on 4562 for depreciation?

You'll enter each of those assets separately in the Assets/Depreciation section.

The fence is classified as a land improvement and gets depreciated over 15 years.

The HVAC gets classified as residential rental real estate and gets depreciated over 27.5 years.

Take special note that neither of those assets qualifies for a SEC179 or SDA deduction per IRS publication 946.

You will want to add as an asset in the rental property section of TurboTax.  Follow the interview and you will be able to file the Form 4562 with your tax return.