You would need to amend all previous years' tax returns. You start with the earliest year so that the unallowed passive losses of each year are carried over to the following year. After amending your 2015 tax return, you can enter the passive loss carry over on your 2016 return.
Please read to this TurboTaxFAQ on how to amend your returns:
https://ttlc.intuit.com/replies/3288565
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