The XML Editor is a convenient way to edit your XML documents. If your XML Document has a corresponding XML schema that describes it, then you can make use of intellisense and more complete validation.

If your document does not reference a schema explicitly, then you can associate one with it see Associating a schema with your XML Document.

If you don't have a schema, then you can infer one from your sample document and use that, see Inferring and XML Schema (XSD).