In what way?
(BTW please turn your CapsLock off - it's considered SHOUTING).
If you're trying to embed a signature in an XML doc, that's easy - put the ASCII or base-64 encoded version of it inside a CDATA section.
If you're trying to sign an XML document so that you know who it came from -- that's tougher. There's some work going on with encryption of XML documents at the W3C, especially for SOAP/WebMethod transactions. I don't think they've settled on anything yet, though.
Chip H.