If your return is still in progress, you can generally get back to your return by logging into your TurboTax online account. You can then click Take me to my return or Continue my return to enter and make changes.
If your return has already been efiled and accepted, you will not be able to make any changes to your original return. In order to make changes, you will need to amend your return. Here is a link that explains how to complete amended return in TurboTax:
https://ttlc.intuit.com/replies/5114064
