How can I pay my TurboTax Online fees? (intuit.com)
But why do you want to file by mail? It will take 6 months or more to process.
First mailed in returns are taking 6 months to a year (or possibly more) to process so efiling is better if you can.
Next ... if you have NOT successfully efiled the return then log into your account, scroll down and click on ADD A STATE to get back in then complete the FILE tab again. Step 1 is choosing to pay the TT fees with a CC instead of the refund.
And.....if you really want to file by mail---
When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s. Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS/state received the return.
Federal and state returns must be in separate envelopes and they are mailed to different addresses. Read the mailing instructions that print with your tax return carefully so you mail them to the right addresses.
How to switch from Efile to mail. This one has a Video
How to mail a return from the Online version
Be sure to attach copies of your W2s and any 1099s that have withholding on them. You have to mail federal and state in separate envelopes because they go to different places. Get a tracking number from the post office when you mail them for proof of filing.