MY WIFE has already FILED HER RETURN, CAN I FILE A JOINT RETURN WITH HER for that same year??

In order to file jointly, you have to amend the return that your wife filed, changing the filing status to married filing jointly and adding your information. (This is assuming that your wife's return was accepted, and that her filing status was not married filing jointly.)

An amended return uses the original return as a starting point. If your wife did not file with TurboTax, it would be much easier to amend her return by whatever method was used for her original return, because the original return is already there. To use TurboTax to amend her return, you would have to first recreate her original return in TurboTax and make sure that it exactly matches the return that she filed.

You cannot do anything with the return that you started in TurboTax Deluxe. You have to add your information to your wife's return.

It's too soon to amend your wife's return now. The amended return forms are not yet available. You also have to wait until her return has been processed and she has received the refund from her original return.

Instructions for amending a 2017 tax return in TurboTax will be available when the necessary forms are available.

An amended return is filed on a special form, Form 1040X. It cannot be e-filed. You have to print it and file it by mail. It takes the IRS up to 16 weeks to process an amended return.