You will need the Forms permission to perform this action.
Navigate to the form and select "Delete" from the "Actions" menu in the upper right area.
You can also go to the form listing and select "Delete" from the drop down menu at the end of the row containing the form you want to delete.
A confirmation message appears. Click on "Yes" to finish deleting the form.
All submissions will also be deleted.
Any payments done during the submission will not be deleted, but it will be detached from the entry. It will still be credited to the person.