XML Canonicalization does not open any wizard or view. Instead, it directly canonicalizes (normalizes) the selected XML document (always the complete document). Depending on the selected menu entry it either maintains the comments or removes them. Removed comments are replaced by an empty line. The XML Security preferences allow you to switch between inclusive and exclusive XML canonicalization, which may result into different canonicalized versions of the XML document (the differences depend on the XML document).
XML Canonicalization always takes place when signing an XML document or verifying an XML Signature. There is no need to execute this task manually (but it does not do any damage in case you do).