You need to capitalize the expenses, add it to your property basis and depreciate it over useful life of the property. When you enter the details for depreciating the property itself, there is a series of questions and entries that you will make so that TurboTax can calculate the basis and the depreciation. One of those questions will be the cost of improvements that were made to the property.
You can learn how to do that here:
How do I handle capital improvements and depreciation for my rental?