Your filed return will be pending until the IRS starts accepting returns on Jan 29 and can not be changed. If your return is accepted you will get an email. If the return is rejected the e-mail will tell you what to correct and you can make changes before e-filing again. Amend to change an accepted return after you get your refund. Instructions below
https://ttlc.intuit.com/turbotax-support/en-us/help-article/tax-return/amend-federal-tax-return-current-year/L7eS6o1qh_US_en_US?uid=lqylnbrx