I inadvertently filed my taxes twice.

It is not possible to file twice.   If the IRS accepts one return from you, any other e-file will be rejected.

you don't. the second should be rejected. however, if the first is accepted and contains errors, you'll need to wait until it is fully processed and then file an amended return form 1040-X. It won't be ready until late February. 

Once you have e-filed your tax return and it has been accepted by the IRS, all other tax returns with your Social Security number on the return will be rejected by the IRS.

Using the TurboTax online editions you can only file one tax return per account and User ID.