Before you remove your information from TurboTax Online you should transfer it to the Desktop (CD) software so that you don't have to enter everything again. See the following FAQ for instructions to switch from TurboTax Online to the CD/Download TurboTax software.
How do I switch from TurboTax Online to TurboTax CD/Download?
It's not necessary to remove your information from TurboTax Online. Nothing will happen with it if you just leave it. But if you want to remove it see the following FAQ. You can clear the information and not start over. But don't do this until after you have saved your tax return in the Desktop software on your computer.
How do I clear and start over?