If you've decided against using TurboTax this year, you can simply abandon your return. If you'd like to remove the information you've entered, you may be able to use the "Clear and Start Over" feature. I'm linking the TurboTax FAQ below that includes those instructions.
How do I clear and start over in TurboTax Online?
*** I am NOT a tax expert. I am a seasoned TurboTax user, and volunteer to provide assistance to TT users. Nothing I post is to be considered TAX ADVICE; I bear no legal liability for responses.***