Since you did not take depreciation deductions on consecutive returns (spanning two or more tax years), your only option is to file Form 3115 (see link below) and make an adjustment for the total foregone depreciation deductions.
https://www.irs.gov/instructions/i3115#idm140516453720416
Note that you cannot simply file amended returns in this scenario.
See https://www.irs.gov/pub/irs-tege/n96-30.pdf and https://www.bradfordtaxinstitute.com/Endnotes/Rev_Proc_2015-13.pdf
Also note that professional tax guidance is recommended when the preparation of Form 3115 is involved.
