As a resident of Arkansas you have to report your income from all sources. If you did not have AR state taxes withheld from your wages you now owe AR taxes.
If your employer does not or will not withhold AR taxes in 2021 then you will need to pay estimated taxes to Arkansas so that you will not owe at the end of the tax year and will not be penalized for not paying taxes.
Go to this Arkansas website for 2021 estimated payment vouchers - https://www.dfa.arkansas.gov/images/uploads/incomeTaxOffice/AR1000ES_IndividualEstimatedTaxVouchers_...
