If you are using TurboTax Online, your data is automatically saved. Once you log back into your account, you should see all the information that you had input already there.
If you are using TurboTax Desktop, from the top click on File, then Save, or Save as.
You can also back up your data, click on the link below for further instructions
How do I back up my tax file in the TurboTax Desktop software?