Ready to mail indicates your tax return has Not been e-filed. You would need to print, sign, date and mail your tax return to the IRS.
Or see this TurboTax support FAQ for changing from mail to e-file - https://ttlc.intuit.com/community/e-file/help/how-do-i-change-from-mail-to-e-file-in-turbotax-online...
