I have a condo I am renting out that cost $x. I understand that I can depreciate this $x over 27 years. Where do I enter $x in turbotax?

You will enter in the Rental Properties and Royalties section of TurboTax.  See Where do I enter income and expenses from a rental property?

Depreciation is the process by which you would deduct the cost of buying or improving rental property. Depreciation spreads those costs across the useful life of the property.