Are you the fiduciary (aka personal representative, executor) for the estate? Are you at all familiar with estate income taxation, distributions, et al? If not, you should seek professional tax guidance and income tax preparation.
The TurboTax product that can be used to prepare an income tax return for an estate (Form 1041) is TurboTax Business (link below). TurboTax Business is not available online nor is there a Mac version; the program must be installed and run in a Windows environment.
TurboTax Business: https://turbotax.intuit.com/small-business-taxes/
You can use the 2018 version of TurboTax Business for an estate that has a tax year of less than 12 months that begins and ends in 2019 and for which the 2019 Form 1041 is not available by the time the estate is required to file its tax return. Note that the return would have to be printed, dates written in manually on several of the forms, and then mailed (the return could not be e-filed with the 2018 version of TurboTax Business).
If you sister-in-law passed in 2019, you could simply select the 2019 calendar year as the estate's tax year and file the 1041 on or before April 15, 2020 using the 2019 version of TurboTax Business (in which case the return could be e-filed).
Further note that an estate is required to file an income tax return if it has gross income for the tax year of $600 or more.
