It means that you indicated that you would file by mail, but have not done so yet.
1. If you are logged into the account you prepared your 2016 return in and are seeing that, it means you chose the File by Mail option instead of e-File or your return is not eligible for e-filing. So you will need to print and mail your return if you choose to file a paper return or you are prompted to mail the return.
This link will give you the instructions on how to print and mail if you are using the TurboTax Online version of the software https://ttlc.intuit.com/questions/1944348
2. Or if you need to switch to e-file instead, you can find the steps to do that below. Click on "Change to e-file your return in TurboTax Online versions" below and it will show you the instructions for how to do that.