If you no longer want to use this return, then you can just delete it.
If this is the only return in your account, you’ll need to start a new return before you can delete your existing one. To start a new return, select “Start a New Return” from under “My Returns”. Once you have started your new return, you can select “View All Tax Returns” from under “My Returns” and delete the unwanted return by clicking the small Trash Can 🗑 next to it (or “Delete” under the return name).