Calculating depreciation for rental condo

I've been renting my condo for awhile and I didn't depreciate it.

 

How do I calculate the cost of the structure vs. the land? If I look at the condo property taxes information from the year I bought it (2014) - I see the land was 20% of the structure. In 2020 the land is 37% of the cost of the structure. Do I use the percentage from the year I bought it, the current year, the year I converted it into a rental?

 

I've learned I should do straight-line depreciation on this number that I come up with above. Where do I enter this in turbo tax by the way? I haven't seen a clear path forward here.

 

Thank you!