You'll need an environment template before you can delete it. If you need help creating an environment template, check out this detailed article.
Navigate to Environment Templates:
Go to the "Environment templates" section from the navigation pane on the left.
Select the Template:
Click on the template you wish to delete.
Archive the Template:
Click on the "Archive this template" button.
Confirm Deletion:
Follow the confirmation prompt and click "Continue" to delete your template.