I sold my vacant rental property in 2/2021. I made capital improvements in 1/2021. Where do I add their cost? Do I add to the cost basis transferred from 2020 return?

The rental property was listed for sale in January 2021 and was not actively listed for rental.  I installed a new heating system during this time.  Where do I add this capital improvement to my cost basis.  The cost basis figure transferred from my 2020 return did not include this improvement as it was made in 1/2021.  Should I manually change the cost basis?  The sale closed in Feb 2021.