How do I use my 2016 downloaded program to file my daughter's 2015 return?

Each version of TurboTax only has the forms & information for one tax year. So the 2016 program can’t do tax returns for 2015. You would need to use a version of TurboTax for the 2015 tax year. Here is what we have available for that year: https://turbotax.intuit.ca/tax-software/prior-year-taxes.jsp#2015