Actually, the FAFSA website has an import tool that will import your data directly from the IRS website. That is of course, assuming you actually filed a 2016 return. On the FAFSA website under the Financial tab that first screen has a "link to IRS" button. Just work that through and it will automatically import all the 2016 tax information for you.
Not sure, but I think it does the same for the 2017 information too.