My scenario is a little different, because I disposed of the rental property this year 2018. However, I will point you to a helpful white paper (also attached).
https://www.natptax.com/TaxKnowledgeCenter/FederalTaxInformation/whitepapers/summaries/Documents/For...
Although old, and the Form 3115 has changed since the white paper was written, I was able (and I think you will be able) to figure out how to fill out the Form 3115. Then, based on similar questions/answers in this exchange, enter the "unclaimed depreciation" on Schedule E as "other expenses" for this year's return.
You will not be able to e-file. You should download the instructions for Form 3115 because you will have to mail a copy of the Form 3115 and the required attachment to another Federal entity, and the address is in the instructions.
Be sure to depreciate this year and all future years - you can only use the 3115 one time.
3115 is not part of the step-by-step - you will have to Open Forms and complete it manually yourself. (Hence the need for either a tax professional or the White Paper). However, when I recorded the Sale of Business Property, TurboTax did correctly calculate the prior unclaimed depreciation using mid-month straight-line depreciation.
