Accidentally chose to file my taxes through mail and I need to know how do I change it through TurboTax to e-file

To change from mail to e-file in TurboTax Online, you need to¹²:

1. Sign in to your account.
2. Select Tax Home in the left menu.
3. Scroll down to Your tax returns & documents.
4. Select the year of the return you want to change.
5. Select Add a State (you're not actually adding a state, this just gets you into the right area).
6. Follow the prompts to switch to e-filing.

I'll assume you haven't actually mailed it.

Did you tell TurboTax you were going to print and mail your return, so now when you log in your return interview is closed?   And do you need to know how to open it back up in order to change to efile?  If so, I'll tell you how below.

NOTE:  I'll assume you didn't actually mail the return after printing it.  If you already physically mailed it, it's too late.

If you haven't actually filed at all, you can open the return interview back up, make any corrections if needed, and change the filing method.  

• Log into your account, and at the Tax Home look for a link "Add a State."
• Click on "Add a State."  (That doesn't really add one; that's just to open the return.)
• Once the return interview is open, if needed you can make any changes in your return you need to, since it has not been filed.
• Then go through the REVIEW section to be sure everything is still in order.
• Then go to the FILE section, progress through the screens there, and change the filing method to efile.
• Then continue on answering all the remaining screens and at the final step click a big orange button "Transmit Returns Now."

This FAQ may also have some info that will help:

FAQ:  How do I change from mail to efile in Online TurboTax?

https://ttlc.intuit.com/community/e-file/help/how-do-i-change-from-mail-to-e-file-in-turbotax-online...