If you prepared and filed your return using the online product, you can open your account and access your return again and do whatever you want with it.
To get back into your return after printing or e-filing, please follow these steps:
1. In TurboTax Online, sign into your account.
2. Select Tax Home in the left menu.
3. Scroll down to Your tax returns & documents.
4. Select 2018, and then select Add a State (You're not actually adding a state, this just gets you into the right menu).
5. Once you're in your return you can navigate around as usual.
If you used the CD/download product installed on your computer, the only copies of your tax return would be on your computer or on a removable storage device if you chose to save it on such a device.