Real estate depreciation reporting

I bought a condo in 2018 and lived in 18 months. Then I moved to another house and rented my condo from 2021. I never claimed any depreciation for my condo and simply reporting rent  - (mortgage  interest+taxes+repair expenses).  How do I start reporting my depreciation? If I don't report depreciation, Can I offset while selling the property? Can you shed some light here. Thank you!