To edit an existing Database Form Template, navigate to the database and click on Edit Form Template.
This will take you to the Form Builder (which you initially created the form with). If you wish to just delete sections or fields, click on each heading and then click the trashcan icon to remove the item.
If you wish to Delete the form and all associated records, the database will have to be deleted, go to the database and select Delete Database, you will be prompted to confirm your request. If you are sure you want to remove the form, click Delete.
*Note this action is permanent and cannot be undone.