For the fafsa, you provide the information for the parent you lived with most during the last 365 days. If you apply Dec 20, you list the information for the parent you lived with most from Dec21, 2017 to Dec 20,2018.
It is likely your parents filed a joint tax return for 2017. If so, you won’t be able to use the DRT to transfer info from their tax filing with the IRS. You’ll have to fill in the info for the parent you live with, and just the income that parent earned. Use W2 forms for that.