With the TurboTax Free product you need to know what slips you need to enter. There is no prompting. If you wish more guidance while preparing your return, there are other products which may be purchased.
If your question is in regards to a 2016 tax return, CRA will already have made the adjustment to include any missing slips that they have on file for you. If you have already filed a 2017 tax return and need to add information then go here: