It sounds like you need a copy of your 2018 tax return to submit to the financial aid office, but you never filed a 2018 return.
As others have said, you can no longer do that with TurboTax online.
To use TT download software (for a fee), see https://ttlc.intuit.com/community/taxes/discussion/access-a-prior-year-return-not-working/01/962519#...
To get free forms from the IRS, see https://www.irs.gov/forms-pubs/prior-year
