Select the Reserved Characters ⇒ XML Entities command in the Characters submenu of the Convert menu to replace the characters <, >, ', ", and & that have special meanings in XML with their respective XML entities <, >, ', ", and &. If you select some text before using this command, only characters in the selection are replaced. Otherwise, all reserved characters in the file are replaced.
Convert menu
Convert|Characters|XML Entities ⇒ Reserved Characters