maybe you can't. the S-Corp loss in 2018 needed to be reported on your 2018 - 1040 return. If you had basis and and enough other income that loss would have offset the other income and would no longer be available. We can not see your returns, so we do not know if you could have had a net operating loss for 2018. if you did, you needed to make an election to carry it forward. failure would require the 2018 NOL to be carried back to 2016 any remaining carried forward to 2017 and then 2019.
unless you know your situation, it is advisable to have a pro go over your situation. they will need to see your returns both S-Corp and 1040 for 2018 and possibly 1040's for 2016 and 2017
if your state taxes S-corp income then maybe the losses for 2018 and 2019 would be available to offset income in 2020