You can delete a CTF added to your site, as long as no data has been imported into student profiles.
Go to School > Data > Import > CTF Import and select the CTF file.
If the CTF is awaiting import, you can delete it using the Delete CTF button on the right-hand side.
If you have imported any new students, or imported data into existing students, you cannot delete the CTF. We would also not be able to delete this CTF for you, as this data is needed for auditing purposes.
Any data that has been imported accidentally should be removed or corrected from the student's profile.